Aside from the fact that it's relatively new compared to other engines, 3D performance isn't quite up to par with other engines yet. I think people are too critical about this, and to be clear, 3D is perfectly capable of doing good looking small-medium games, but you'll definitely run into issues if you're trying to do something very high-end.

Vulkan support is currently being worked on and will be added in Godot 4.0, which will come with many performance improvements as well.