Hmm, as far as mass appeal goes, I'm generally pleased with whatever results I get, you know? Like right now, I'm at a good point with my work. I have an active audience asking questions, they're generally excited about my plots, and they look forward to the updates.
Granted, what I do really isn't mainstream, which ties into the next question. I work with a lot of sub-genre horror, (cosmic horror romance, paranormal romance, and folk horror currently). These are very niche markets, as far as mainstream stuff goes. Hell, we barely have a lot of monster romance movies that aren't just vampires and werewolves. But I think what kinda helps me is having a not-so niche art-style. I also do a lot of bonus content that's light-hearted and have inside jokes that most people can get behind.
Truthfully, I don't think something can be too niche. But I do think something can be too cut-off. Lot of the times, the reason things don't get popular isn't because it's "not good content". It's because it doesn't really sell itself to that bigger audience. It doesn't try to connect with them. I work in cosmic horror romance with Our Universe, but many of my readers normally read mainstream romance comics. What reeled them in? The relationship between Brenda and {REDACTED}. The love is real between them, and the stakes are high -- just in a different way. And I did it in a way that allows room for wholesome vibes between the horror. As a result, people kinda like my work, and they tell me they look at other cosmic horror content because of my work.
If you can sell it and sell it well, people will buy. It's just a matter of how you go about that.