i’m completely serious.
if you’re having trouble coming up with new, distinct characters, then a good thing to do is take some breathing room and distance from your own characters, but still keep practicing your work on someone else’s. find a very large cast, and write about as many of them as you can. naruto? one piece? suikoden? dorohedoro? DC and marvel? etc, etc. anything that has a very large cast with distinct (if sometimes shallow) personalities. hell, it might give you even more to work with if they are shallow - that gives you more room to practice your stuff by fleshing them out.
this takes away the intimidation of creating your own characters and the worry that they’ll be all the same, and lets you practice your writing and branch out your skills, develop your range, and make many characters. make sure you especially include the kinds of characters you wouldn’t normally write.
beyond just that, when making a character, if you’re shaky on how to make them distinct, start writing their history. not just their “origin”, but their history. little things. big things. how their family influenced them, how their life influenced them, the people they met and how they influenced them, the events they came by or caused themselves. as you write their history, you will also inevitably create other characters, who you can also dive into and flesh out and give their own history, practicing your skills and making tons of other characters you can use now or later too! also helps give you lots of opportunities to create a more inclusive and wide-ranging kind of cast.
and hell, remember - warren ellis tends to keep writing some kind of variation on ‘trenchcoat genius asshole is an asshole genius, and people love/hate them’, and he’s made a viable career on that. you can find inspiration anywhere!