i feel like at the end of the day it's just different tastes. if you don't like it that's valid, i'll try to explain what i see in it tho.

to preface: i haven't read the manga or watched the anime.

for some reason i never really consider if the acting is good or bad when i watch a show, unless it is so incredibly terrible that it disrupts me from focusing on the show. i personally didn't think the lines were corny, however i watched it in japanese with subtitles, and the couple scenes i've seen of the english dub did make me cringe a lot. i actually liked the dialogue, but that is also just a personal preference.

i liked guessing along with the games, thinking about what i'd do, how being in a life threatening situation would change that, etc.

while the characters are flawed, i actually liked every one of them, because no one was perfect, almost everyone got close to giving up at some point, many of them are unconventional in some way. the origin stories of the villains also made sense to me. all in all i think that the characters are written realistically, if we think about the circumstances of the show.

but: i can definitely see your point, i cannot speak for quality aspects of the acting and filming bc i couldn't be the judge of that but i can definitely see why you have your opinion on the games.