Godot 4 removed the GLES2 renderer, and the C# export for Android/iOS/web are still experimental due to the migration from Mono to .NET. Those already block a lot of people from upgrading.
As for GLES2, the devs originally convinced themselves that a Vulkan-only renderer for Android was viable on the current market, but they had to backtrack and add a GLES3 "compatibility" renderer, which AFAIK has also proven insufficiently compatible with actual low-end devices.
