funny then that none of your exemple except demon slayer work that way
MHA is about the near entirety of humanity (it's supposed to be 80%,but it's easy to forget when the author doesn't do anything with it) having random powers and some of them being deemed good enough by an arbitrary ranking boss fight to make them heroes (the entire start of the series even talked about how unfair the focus was on powerful physical powers etc,but it was also badly written if you remember half of the students being incapable of actually winning the robot fight,and now it devolved into end of naruto bullshit and every hero being a private cop isn't even adressed anymore or just in passing and handwaved)
for Jujustu Kaisen,one of the strongest characters is because of their lack of genetic inheritance,the MC has powers because he's possessed by the strongest demon that ever existed,and every family shit on the respective characters as "not belonging to the clan",one of them is litterally a spirit robot built by someone who then made it his son,pretty much all the families are deeply disfunctiunal and it's honestly quite dark and pessimistic on the family question,where they all end up killing each other or losing one or more relatives.
For Demon Slayer,the MC isn't strong because of his family,one of the character litteraly lived in nature and trained there,but I do agree that a lot are descended from old slayers (but it make sense,because they're the one who trained their children) it's not necesserally about their bloodline except for the thunder guy,where yes,he wouldn't have his power without being born from his family.
I do agree that powers that you can only inherit is pretty lame,but that's Dragon Ball Z+Super you're talking about (or AoT,but it's subverted when talking about the Hackerman,and the time travel bullshit)