ok i used to have this same problem and i have some solutions for you to try. if you have 8gb gpu or higher make sure textures are set to highest cause for some reason that can cause stuttering. disable high functioning dpi and full screen optimization in the compatibility tab for destiny2.exe those two things made my game run so smooth i was shocked that's what it was

Seriously man, like I really wanna get into this game but I just can't get over the fact it feels like 45fps. I'm getting like 80-130 fps and if I didn't have an FPS counter, I would be thinking I'm stuck in the 40s. The mouse movement doesn't feel bad at all, but the game just doesn't looks smooth and pulls me out of it