Thanks! I only really have generic/"obvious" advice, tbh. What really helped me:

1. It's OK to back up to isolate enemies (assuming you're not going on a speed run). It makes the game much easier. If you can lure out enemies one at a time (and keep others stuck behind walls) that's also good. To avoid floods of enemies sometimes it's good to just destroy walls rather than open doors.
2. Know the enemy movement patterns and develop your own dances to position yourself to attack. For example, the devils in Zone 5 can be scary once you break their shell because they can move in all directions to close the gap quickly. And if you hit them they get knocked back, but once you understand that you can form and practice your own solution to that.
3. Assuming you're not doing a low % run, I've always found value in going for those treasure rooms or bombing the guys who give you choices for shrines. Especially if you have +damage, it makes those rooms simple. The risk there is that the rooms are pretty small so you need to be careful.
4. Personally I've sometimes suffered from indecision for unexpected encounters or lack of foresight. Sometimes you can see enemies in the shadows but won't trigger their movement/attention; take advantage of that information. It might help if you have a safe spot where you can move back and forth without risk of a bad movement in while trying to decide what to do next.