The real reason Second Life runs like crap is because everything is user created, not all creators optimize their meshes/textures for “gaming”, and SL has no hard upload limits. Ex: a typical avatar in a tripleA FPS will be around 15k-20k polygons. In SL, an avatar can be 5-10 times that and more!😵‍💫

And to add to this, locations in SL may not be built optimally either, where the builder will use assets made by many different creators which fills up your texture/object caches with unnecessarily unique data. Most AAA games use the same assets throughout the entire game so client load is lighter.