The best things (at least I feel) that I've made for DT3 have always come after I have internal battles with myself about it or a big decision regarding it. I've typically found the harder decision to make to be the better one. I don't mean in terms of hard to execute, but something that has potential to be controversial. To go more in-depth with that word, I don't mean culturally or socially controversial, but simply within the game itself. (Though it does dive into a few harsh things from time to time, unlike its predecessors.)
The end of the game, not the ending itself, but the entirety of the final sequences has been a fight for me since the project began. There has always been a specific way that I've wanted to end the trilogy. Both in gameplay and story. Now that I've been actually making these final bits and I see that original plan going through, I'll be honest and say I'm super happy with keeping with my first thoughts. There's been many times the past few years that I've thought to end the game another way because another idea would be more what's expected and better received. DT3's development has been more mindful of the end user than DT1 ever was, and that's not bad at all. But when it came to big decisions, and deciding to go with what could be better received, I preferred to go with my way.
While DT1 is super flawed in many respects, doing things my way worked out pretty well for the game in a lot of ways. Some of its more odd decisions had some of the best responses. That's not in itself a justification for it. I've found that if I'm happy with it, regardless of how it's received, I like it.
Something I did give in on, was including easy mode into DT3. And almost immediately after, I thought, 'I should disable easy mode for the Nightmare levels.' I've fought with that idea. Even some of the testers mentioned that could be a thing. I don't think the conversation itself needs to be cited, but I did turn it down, despite already thinking I should do that anyway to preserve what I initially had. Easy mode isn't something I really wanted to include in the game, however it is staying and I understand its utility. That said, it is going to be off-limits for the Nightmare gates in the final version, including what they lead up to.
In the decisions for the game when I was conflicted, nearly all of them came down to how I felt about it and no other metric. I made DT1 for fun and to be this thing that was mine, I've always felt my best stuff is when I go with that. The game is, in the end, something I want to make and nothing else.
I'd like to make a note that this isn't against my testers or critique/feedback from them. That's a whole separate thing from what this post is going on about. They've provided a countless amount of help. There's a TON of little things, nagging things that would annoy the player, that if the testers weren't around, would still be there. And in some cases, big things that have impacted the game in a huge way have come from them.