And as someone who was introduced to D&D “back in the day” may I simply suggest this:
If you do not like the content being produced, simply do not purchase it.
My family, friends, and now children have happily played D&D for decades with minimal purchasing of actual product. Simply using the basic framework and creating our own character classes, monsters, NPC’s, and quest modules. Of course it helps that we have quite a few creative and mathematical minds that can extrapolate from the basic manual, but the result is quite fun, quite cheap, and I don’t provide financial support for any material I find objectionable.
The key is finding (or being) a DM that runs their dungeons in ways acceptable to the group. If you don’t want demons, then have a DM that keeps to non-spiritual antagonists. I run one group that really doesn’t particularly like fighting - so I keep the battles to a bare minimum and dial up the level of mysteries, puzzles, and physical challenges (coming up with ways to cross a flooded gorge using minimal tools and resources, coded messages, shifting labyrinths, etc.). That group mainly earns their XP’s by solving problems and finding/earning treasure by helping other NPC’s with their missions rather fighting. There are a few giant rats, wolves, and the occasional goblin pack to keep things interesting but no dark forces, curses, or magic beyond the traditional spells are involved.
I have no thoughts about the particular supplement you’re talking about. It may be fine, I leave that judgement up to the individual. I’m just saying you can easily play this game without getting into anything you find objectionable.