MAME literally scans the dies to read the chips and understand their logic. FPGAs faithfully recreate this as well. and no, you can still run a 8bit micro on whatever display you want. Projects like dolphin and BSNES documented the hell out of everything they do with a goal of accuracy in mind.
Recognizing a problem doesn’t put down the developers who will have to work on it, rather it highlights how important their jobs are and how valuable they are as a resource!
I believe there are some psx test Roms that no emulator gets 100%. I know for a fact there are n64 test Roms that don’t get close on an emulator.
You point on hardware emulation stands regarding it doesn’t automatically mean more accurate emulation. Although it lends itself to be more accurate due to you “can’t make a software thread for each discrete component” software problem as well as “how do I take controller input and when” as well which are wayyyy easier on fpga than software.
Not really (and you don't always want perfect accuracy anyway).
You don't only need to validate the operations of the machine, but also the timing with which it operates.
And I don't mean just the clock/frequency/operations-per-second - it's everything.
Every little chip that performs a calculation, every little wire that sends a message.
Not a popular game, but the cartridge for Morita Shogi 64 had a built in RJ-11 jack and allowed online multiplayer.
Plenty of SNES games included a SuperFX graphics coprocessor in the cartridge. Star Fox is probably the most popular example. SuperFX games were popular enough that it was quickly emulated successfully. But you can't treat the cartridge as just a file system abstraction on SNES.
The instruction timing and such fiddly low-level details is most visible in systems programmed in low level, such as older consoles.
Modern systems tend to be programmed in higher level languages, which works much better to HLE (high-level emulate), since they tend to be programmed in a way that cares less/not at all about underlying hardware fiddly details.
So when you are emulating the NES, these details matter way more than when you are emulating the Switch for example.
As well as that, many people are decapping entire chips and games, just for exact emulation. So, no, you're talking out your ass, sorry.
Hardware emulation isn’t a solution. An FPGA emulator isn’t intrinsically more accurate than a software one, and documentation and schematics that are used to implement emulators can be incorrect and don’t specify ‘undefined behavior’ which was very much used reliably by software developers.
The approach adopted by MAME has proven to be the only reliable: you have to measure some output on a real working system and compare it to the emulator behavior, but this can be impractical and becomes moreso over time as systems become more difficult to operate. (E.g. I can’t even operate most 8-bit computers without some kind of mod because I don’t have a CRT television anymore).