Balance is the group feeling challenged and feeling accomplished when they overcome challenges.

That's why I use the D&D books as a basis but then ignore the lore parts and modify the stats to fit the story I want to share.

I've "taken the next step" before as you put it but it's a lot more work and not every player is comfortable with an untested system that may have massive probability or metagaming blind spots. To put it another way, I do what works for my group.