Quite good actually when you use the forward+ renderer (vulkan) and do the little things properly (using multimeshinstances or shaders heavily instead of tons of direct meshes, using occlusion culling properly, making sure you have multi-threading enabled, run physics on a sep proc, etc). I'm evening running with full dynamic global illum and loving it.

I'm not trying to prematurely optimize but my game worlds are very large, (I have a working to scale earth for example) (oops, forgot to mention, to get good large world behavior, compiling with double precision is a must! (https://godotengine.org/article/emulating-double-precision-g...)) so I've been watching lots of GDC and other talks from AAA titles and how they do their rendering pipelines, and my conclusion is that shaders are really the powerhouse of gamedev these days and anyone interested would do themselves a favor to start learning the quirks of your engines shader language now.