User blog comment:Ddlcmc/Hey! i know the drawback to shoto's fire quirk!/@comment-32705196-20180406215124

That's a logical explanation but it isn't official, although the only weakness we can say is true for sure is that he depends on his Quirk way too much like Stain says which leaves him vulnerable since he has little to no physical abilities compared to people like Bakugo or Deku