See, now when I do play it, I'll have the whole series just waiting for me. Smart, huh?
I've not got a steam deck so I'm going off general knowledge here. I think it's a bit much for the thing. I know it runs because my friend is using it to play but he says the graphics definitely take a hit. The game probably uses a hidden ultra-low preset.
The nature of the game really begs for stable 60+fps and quick Google says it only hits 45 at most on steam deck. Probably why my friend is struggling.