[2021] Annoyingly stuttering both with and without VSync

By default, the game renders the scene as many times a second as your hardware can produce. You're right that there's not much to render at the main menu, so you get a really high framerate instead. This might be different in Windows, but for me in macOS and in fullscreen, turning on the game's VSync setting in Video Settings -> Display keeps the framerate at the main menu sane. E.g. it doesn't run my GPU as hard as possible just because it can.