If your ultimate goal is to create your own fiction and draw a story (be it a comic, webcomic, visual novel, etc) then I suggest you buy these books by Scott McCloud:
This author approaches the subject of storytelling from the perspective of comics as the title implies but everything he talks about can be applied to visual media in general, so while it won't teach you to draw point by point, it will give you great incentives on what you should be focusing on when drawing characters, backgrounds, and events that serve a higher purpose for your story.
Regarding character design once more: I believe your only fault is a lack of focus, you have a lot of ideas based on personality traits that you want to execute on different characters that you don't give yourself the time to flesh out a single character from the ground up, which is why you end up using the same core characteristics you have already practiced anatomy-wise (in this case: slender bodies with long limbs, big eyes, thick hair, and sharp features) so you could show personality as quick as possible. This mistake has nothing to do with style, it's just what happens when an eager artist gets swayed by first impressions from awesome characters and never looks beyond the superficial details, ignoring the underlying structure that defines the characters themselves. Consider the following:
Shared traits and characteristics between characters:
1) Biological: Specie (overall physiological properties), race (physiological properties due to environment or heritage), gender (physiological properties due to reproductive role), average lifespan, average height, average weight, average skin color, average eye color, average hair color and length, average muscle growth, common illnesses and diseases, physiological needs (eat, sleep, excrete, reproduce).
2) Psychological: Common emotional response under similar conditions (for example: success = happiness or satisfaction, failure = sadness or anger), intellectual capability under similar conditions (for example: two people educated on the same job will yield the same results in their average work), common mental disorders due to genetic heritage or physiological deficits and trauma, common personality quirks present in the specie as a whole (are we all prone to become perfectionists at some point?), common psychological development through age and growth.
3) Social: Language, ethics, morality, laws, customs, traditions, religious beliefs, education, clothing trends, food trends, technology trends, careers, economy.
Traits and characteristics unique to characters:
1) Biological: Current age, gender identity, current height, current weight, current hair color and length, current health condition, current muscle growth, current body integrity (did they ever lose a limb, adquired any scars or spots, adquired a genetic condition that handicaps them, or their overall body is limited by something that only defines their peak health but doesn't equal illness?), physical asymmetry (what are the little differences in their limbs and "symmetrical" body parts?)
2) Psychological: Current emotional response, current intellectual capacity, quirks that repeat on average indicating a possible disorder (for example, are they obsessed with being clean or with symmetry? do they crave other's approval no matter what? do they deeply enjoy other's suffering?), quirks that repeat on average abiding to a personality archetype (are they diligent in their work? are they loyal to family or friends? do they stand up to injustice often? do they love to learn and study in silence? do they enjoy loud company and reckless fun?), current psychological developtment compared to their age and growth (are they a prodigy for their age? are they lacking for their age?).
3) Social: Current known languages, current skills, current education, current social position, current economical position, current ethics and morality, current customs and traditions, current hobbies and preferences, current taste for clothing and accessories, current home and social identity, current spiritual beliefs, current career.
It might seem a bit out of place to talk about all those details (which are only a part of the many things that define a character) considering you are interested in fixing your drawing skills right now, but the reason I bring them up is to let you see the subtle differences between them and how they affect your focus at the moment you draw. At your current skill (and based on the drawings you have shown us) you begin drawing the head's shape and build from there until you finish the hair, eyebrows, eyes, mouth and shoulders; ignoring the ears and the nose in favor of your current style. In here you already try to use those details to convey some emotion or personality which means you are not focusing on the anatomy at all. However, it's past the shoulders when you unconsciously forfeit the character's body and choose to finish superficial details like clothing from the get-go, which forces you to decide on a clothing style before you even have a body to dress, switching your focus from the character's anatomy to their social statement entirely. With your focus on clothing your mind turns anatomy to "automatic", filling that requirement based on what you have learned so far without trying anything new so that you can keep on focusing on the surface. You define the limits of the shirt or hoodie with no defined limits of the torso itself and end up creating an accessory of clothing that fits too tight (given another pose it would not cover that body area properly), and because you haven't learned any other body type you automatically made a thin "invisible" torso again. As a plus, since you drew the head from the same perspective or position you find yourself with a limited degree of how you can pose the rest of the body, meaning that when you go automatic with the anatomy you can only choose between a standing position or slightly bending the outer limbs to create a bit of contrast with the middle part, but the result is still a bit stiff. You finish the structure by using jeans as the defining characteristic that will limit the character's legs, giving them a tight fitting as well while automatically going for that thin and long shape, until you reach the feet which are completely ignored and replaced with featureless shoes. The arms and hands are used to contrast the stiffness and convey some personality at the same time but they are not enough to support the characterization, and you don't notice it because you are still focusing on the accessories and cosmetic details that will give that character a superficial difference compared to the previous characters drawn. On their own, these choices are not a mistake since they can be used well (remember Shaggy from Scooby-Doo? that guy had a design similar to the one you use and it became iconic), but you let them become your "automatic" response to drawing in general because you are not focusing in the anatomy behind the characters.
Suggestions on how to fix it:
1) Don't think about clothing, accessories, or facial features, until you have sketched the whole body of your character and the position you are thinking of drawing. Remember that stick figures and circles can go a long way.
2) Every time you wish to draw a new character abide to three different perspectives: front, back, and profile. Create a grid that will measure their size and proportions, the normal unit of measurement in real life drawing is the head: for example, an average adult human male has the height of 7 1/2 heads (their head) by 2 heads when standing right. This can be used as your reference drawing for future depictions of that specific character.
3) When you are done drawing a specific body type try doing a quick sketch of an opposing body type in the same position you are using, for example, draw any of your current characters as a chubby little guy and then try drawing them as a bulky giant. This will teach you the difference in size and shape.
4) Use the shadow test to check if the characters can be identified by their silhouette, just ink the whole character in a single color and put them side by side with no linework showing inner details. If two characters seem too similar, ask yourself if they are supposed to look the same and proceed based on your answer: if they should be identical they are either clones or twins, and even then they should have a distinctive feature so we can tell them apart; if they should be a bit similar they should belong to something that justifies it, like an army or guild that demands a specific set of characteristics, but they should be different at some level other than color or accessories; if they should be different change one of them from the ground up.
I hope this can help a bit in your endeavor, once again I wish you good luck and aim for the best.