Zero isn't as bad as people make it out to be, it's just that by the time it came out, people were sick and tired of tank control survivor horror games to death. This is one of the big reasons why Resident Evil 4 was such a hit, I think RE0 really needed to re-invent the wheel in a similar way to keep the genre going and a shitty two player mode wasn't it. Game would have been a lot better if it was a safer title, ironically enough, letting you select between two characters like the first game did with Jill/Chris and the other being an NPC, and while the entire game couldn't take place onboard a train I feel like we could have had a more unique setting than just the fucking mansion again. RE Remastered was coming out around that time so it was twice as redundant, similarly to RE2/3 taking place in the same fucking city.
I dunno what they could have done to make RE0 more than the last dying breath of the genre before RE2R and RE7 kind of re-invigorated it years later, but I won't join in shitting on it. RE0 could have been a great title, but it wasn't and that's that, it certainly didn't kill the franchise or the genre.