You need hardware for these things. High speed image processing and high precision control and global shutter cameras. You can't just slap a raspi on it with any run of the mill camera and call it a day.
Hw access is also not as easy as you think. Try getting a Pixel 9 class SoC board that you can actually dev stuff on, you'd be surprised how hard it is to get such a thing. And when you get it, it will probably be 2x as expensive for just the board.
Oh, put the Pixel 9 on it then. Have you tried doing optical flow on rolling shutter cameras?
Then, whatever solution you get, you need sufficient volume and reliable supply of the thing. Oh, you can't find the chip anymore? Good luck porting the stack you have since the pipeline is different.
Whereas these rc FPV drones you can basically build what what you find in the back of your drawer.