This is no use for VATSIM or IVAO, but if you get a lot of “Generic” aircraft mentioned in MSFS ATC comms, you can actually re-name them by editing the aircraft.cfg file for each generic plane in your LocalCache\Packages\Official folder.
Scroll down the list of aircraft to:

Asobo-aircraft-generic-airliner-quadengines
Asobo-aircraft-generic-airliner-twinengines
Asobo-aircraft-generic-piston-multiengines
Asobo-aircraft-generic-piston-singleengine
Asobo-aircraft-generic-privatejet
Asobo-aircraft-generic-turbo-multiengines
Asobo-aircraft-generic-turbo-singleengine

You can use any name you like to replace “Generic”, but I’ve used the ‘most likely’ type based on the model appearance and/or a flyable type in the sim.
Open each aircraft.cfg with Notepad and under the [GENERAL] heading, look for:

[GENERAL]
atc_type = “$$:Generic”
atc_model = “$$:”

The model name for Generic planes isn’t used by ATC, so I’ve only changed the atc_type as follows:

Airliner Quadengines: atc_type = “$$:Airbus” ← looks like an A380?

Airliner Twinengines: atc_type = “$$:Boeing” ← probably the most common twin engine airliner?

Piston Multiengines: atc_type = “$$:Beech” ← similar to the Baron in the sim?

Piston Singleengine: atc_type = “$$:Piper” ← looks like a Cherokee?

Privatejet: atc_type = “$$:Cessna” ← similar to the Citation in the sim?

Turbo Multiengines: atc_type = “$$:Beechcraft” ← similar to the King Air in the sim?

Turbo Singleengine: atc_type = “$$:Pilatus” ← looks like a PC-12?

This makes a noticeable difference in the sim and has no effect on Simple Traffic or FPS.