The best way I can describe Demon's Souls is kind of like the single player version of EverQuest. Or one of those cryptic movies that doesn't give you all the details of what is happening (Jacob's Ladder-ish?).
The mystery and the difficulty are what make these games; it may not seem like it right now (I felt the same way as you at first), but I swear - one day it just "clicks" and then you can't stop playing.
For me, I tried DS1, gave up. Picked up Bloodborne, ended up platinuming it and then beating DeS and DS1-3. Can't get enough now.
Oh, also, I'd argue the combat is more intricate and in-depth than any other game series - it's just somewhat hidden. There's parrying, blocking, dodging, and it all means far more than it does in most games. A missed parry or dodge or block can cost you 30 minutes, and you get better each time.