Yes quixel assets are fine for a game.
However it is very easy to go over budget with texture sizes and vram (graphics card ram) size.
So unless your game is aimed at only newest cards with lots of vram, and PC that uses ssd m.2 drive, you kind of must limit textures.
All (or most of them) quixel assets use skin like textures, which means each mesh will have 4 textures (diffuse/color, normal map, metallic and so on). You need to manually process them to limit ram needed. You can also use layered material that reuses same textures, and just mixes them on quixel mesh assets.
However if you starting game, do coding first with minimal assets. You need git or perforce server, they have limited space. And updates downloads will be much slower with huge quixel textures. So save time and develop game on tiny level that has minimal size of meshes and textures.