to be sure: you see 2fps only in that loading screen ?
If so, then you topic is a duplicate topic of:
and not an issue at all. Nobody care about fps in the flight-load-screen.
If you mean low-fps in generall, then please share real-fps value while you in-flight, only these is relevant. There are also lots of topics releated to such cases with existing hints. As example most important is tLOD setting and some times makes photogrammetry bit trouble near ground.