You don’t wipe down your microwave
Hate cleaning your microwave? There’s a reason for that. Food left to dry and crust over is pretty difficult to remove.
The solution is simple; wipe up spills as soon as they happen.
If it’s too late for that, heat a bowl of water in the microwave for several minutes until steamy, let it cool for a few minutes and carefully wipe the interior. The steam helps loosen stuck-on gunk.