My big problem with Tahoe, is the lock screen animation stutters and freezes CONSTANTLY. I'm on an M3 Pro. If I can watch 4K video with no dropped frames, a simple video background should work as well, and if it doesn't, it shouldn't exist.

Are you using a Studio Monitor? Lock screen videos are incompatible with Settings > Displays > Refresh rate > Adaptive. You have to use a fixed frame rate (60 or 120 Hz).