I've found some games that require attention to close detail or your surroundings are a struggle to play on the deck. Metal Gear Solid 5 is a recent example that comes to mind, and Sifu as well. Both require being constantly aware of what's around you, and with the 16:10 screen, I feel like the games are much harder than on my PC (21:9 ultrawide, and big display). With MGSV in particular, it's a bit harder to avoid patrols and keep track of everything, and with Sifu, I get enemies sneaking up behind and hitting me when I would have definitely spotted them and dodged on PC.

Also, due to the lower res screen, even though it's small, in some titles I find fine detail suffers, like spotting hidden items or whatever.

On top of the above stuff, I also find it's a bit hard to work the L1/R1 buttons at the same time as the triggers due to their placement. The bumpers are way higher than on a normal gamepad like an Xbox or 8BitDo controller.

For this reason I find myself gravitating to other gaming styles on the Deck, like racing, 2D indies and RPGs, and linear stuff when it's not so essential to have a complete focus on everything, if that makes sense. Shooters seem fine for the most part, but 3D action games not always.