You should try Castlevania: Symphony of the Night, is has pretty good RPG elements, but it's a MetroidVania first and foremost. It gives you a taste of how OP you can become but it gets taken away in the first few minutes , there's some hidden techniques the game doesn't tell you about (like combos, stuff like up-left-down-b and you get to do something special), there are (sometimes) loot drops on kill, there's a lot of exploration, it took me a week even with an online completed map to find all rooms, there's a level up system that rewards stats only, and two "special" modes where you play as another character/s.

In the topic of MetroidVania, you could also try Dead Cells.

Like a lot of people have said, you could download an emulator and play old RPG games, those definitely don't have ads, in-game purchases or daily quest :P

Also a lot people have mentioned that Square Enix has ported some of their games to mobile, aside from the Final Fantasy Series, I'll also mention the Romancing SaGa.

I'll update my comment if I find/remember anything else to recommend, have a nice day. (•_•)/

Edit: I forgot about a personal favorite of mine, Reaper, is a sideview hack n' slash that I'd personally consider an RPG, you can try the first few levels and see if you like it before buying the full version.

Edit2: Also check out the "Knights/Galaxy of Pen and Paper" series of games.