And every Unreal asset flip has these high quality renders that turn your GPU to 120%.
Quixel is more of a curse than a blessing.
Sorry, I don't need rocks to have 1000 polys and 6000x6000 UltraHD realistic textures.
Actually 90% of the time, Unreal burns your GPU because by default Vsync is off, and Unreal without Vsync just maxes out your hardware usage no matter what. Whats worse is that to turn on vysnc you need to run a console command, so all the shitty asset flippers don't know this and ship with Vsync off.
Quixel is really nice if you just need an asset quick, but if you are actually making something that isn't "Hire this man" graphics you need to actual author your own materials. I mainly just use Quixel stuff for Blender renders, since they look good when you raytrace, no extra work. For actual Unreal stuff, I use Mixer to actually make unique materials out of the Megascans stuff, and I usually stick to 2k textures, since you can easily get higher detail with detail textures (Unreal Engine 2 did this, its not new but nothing does it anymore). Texture file size grows exponentially, 4k is 4x the size of 2k, and games are being rendered at 4k now, which means you 'need' 8k textures to not see texels.
The 3d scanned stuff I usually avoid, since for natural stuff it just looks like a blobby mess if you don't download the 8k source scan, and mechanical stuff can easily be modeled by hand and have proper topology instead. I do use the plants though, since those aren't 3d scanned, they are authored by an artist at Quixel, but use the scanned plant textures. Epic games is a shitty company though and they released the trees, which are the same deal as the plants, but ONLY for Unreal, which I have better options for that don't alias like crazy. I would use the trees in Blender, but I literally can't.
Modern hardware isn't really limited by polygons anymore, they can still be an issue if they are a bunch of separate draw calls, but GPUs have advanced to be able to render millions of tris. The issue stems from devs not optimizing anymore, probably because publishers want the games out as soon as possible for maximum money. It doesn't help that nobody is learning about optimization anymore since everybody is just using a pre-made engine that does culling and memory management for them. I've seen mods for Skyrim that have the worst texture optimization I've ever seen, single colours stored at 4k and the like. Whats bad is that modders are moving towards indie game dev, but they are taking their non-existent optimization skills with them, leading to messier games. Modern hardware also doesn't help, since for the most of the time you can just throw the poor optimization at it, and the hardware power will make up for it.