Why would you use FPGAs instead of either trying to make the emulation better or fixing the code to work on new instructions.

And yea modding roms is more difficult but not as difficult as a. Trying to learn how the cpu on these old consoles function b. Learning how FPGAs work c. Programming these fpgas to worn like old consoles.

Only the dev team needs to know FPGA design. Not everyone. Just like the otherway. Someone needs to learn how to dump the ROM and probably needs to design hardware for it. Needs to dissasable it, edit the resulting mix of probably really special assembly (cause of special hardware) and then be able to compile it again.

Sounds much easier to do for every single ROM then designing the FPGA...

but since everyone has those skills that should not be a problem /s

Emulators are a nice middle ground. They are allowing to emulate the environment and you only have to create the emulator once and all/most ROMs are running. But still are not able to reflect the game to 100%. Talk about that to the speedrunning scene on older hardware. Some quirks/bugs/specific lags are not there.