I think it depends on how it's done. In a Somburliss story, where "bad end" just means "go back one choice after you read this fun chapter", I think they're really great and add a bit of fun for people who want to see different stuff. I don't super like it when it's more the sort of "abandon all of your past choices and restart again" bad end, though.
I feel like some people who do Game Mode stories feel like they need to punish the readers who don't succeed at the objective, like real games do by sending you back to a checkpoint, but WAY overdo it and force you to start the whole story over. People are here to have fun, and being forced to scroll and click through twenty chapters again, without reading them because they're identical to last time, just to have another try isn't fun or challenging. Especially when the bad end was a "pick-a-door" style bad end, where you really had no control over it and getting the right answer isn't rewarding.
So, I'd say that bad ends can be good, but they need to be easily rewindable/not needlessly punishing. I think sometimes people can forget what readers are here for, and end up following aspects of similar-but-not-the-same media a little too closely. The same goes for actively punishing people who read your Game Mode story out of Game Mode, or being weirdly mean to them with author's notes, which I've seen a few times. Even if you don't wanna take time and go out of your way to make it accessible and understandable for people out of Game Mode, you don't need to be mean!