Is there any reason for why the FPGA couldn't just be replaced with for example an on-device generic ARM SoC like an RPi pico/nano doing the same in software?

Is there any reason for why the FPGA couldn't just be replaced with for example an on-device generic ARM SoC like an RPi pico/nano doing the same in software? Or is that how far your purism in anti-emulation goes? (;