There’s nowhere near as much traffic in game as in real life. And atm it would seem that Live Traffic is working about as well as Live Weather - either not working very well, or only working sporadically. That too can be verified by using FlightAware. It will show you all flights (commercial, military, private) that are being tracked by ATC over the entire planet. Typically, I’ve found that we only see about 10% of real world traffic in game, and it gives priority to airliners (and typically certain airlines depending on the region you’re in) over small GA aircraft.
However, real world GA aircraft do appear in game as well. If you see a small plane taxiing, take note of the ‘name’ in the name tag. That’s actually the real world plane’s tail number. You can look that up in FlightAware and it will be there as well. It may not be the same type of plane you see in game, but will typically be of the same class (like small single engine prop, dual engine prop, business jet, etc).
If we heard other people “talking” to ATC, you’d hear all kinds of call signs like Timmy Air 69, Bob’s Bonanza 45, etc. You never hear that. It’s either real airline flight numbers or “Generic”. And like I said, 100% of those Generics (if you can get their full tail number by seeing their name tag) are real planes in the real world.
I can understand this can come as quite a surprise when you thought all those other planes were real people playing. I thought so too when I started. But there’s no reason to take my word for it. Everything I’ve said can easily be verified via FlightAware and confirmed as correct.