FlightAware is mostly US based coverage, and not every plane seen from their web site feed is portrayed in the sim. In areas outside the US, the coverage can be sparse.
AI and ATC need work, you see this when an AI aircraft is ordered to Go Around, it just flies past the airport, circling at low altitude instead of performing a Missed Approach.
That’s why I bought Aerosoft Simple Traffic. At 35 percent slider using Offline AI traffic (injected by Simple Traffic), you get historically accurate flight plans, volumes of planes, full gates at major airports, and correct Livery. You will take an FPS penalty, but you can adjust it to taste. And you’ll actually see Departing Traffic if you’re at a big enough airport.