Rear Admiral: The end is inevitable, Maverick. Your kind is headed for extinction.
Maverick: Maybe so, sir. But not today.
Bradley 'Rooster' Bradshaw: My dad believed in you. I'm not going to make the same mistake.
Amelia: Captain, still?
Maverick: Highly decorated Captain.
Maverick: He would always resent me for what I did. Why should he resent her too?
Maverick: You think up there, you're dead, believe me.
Answer: The real-world answer is that F-35s only come in single-seat configuration, so there was no way to put the actors in one seat for filming while pilots flew the plane. It would also make for less of an "underdog" feel of going up against overwhelming odds. The in-universe answer is that F-18s are better suited for the kind of mission it is.