The Stan Lee cameos can’t last forever, and Endgame was the right place for them to conclude.
There’s real closure to Stan Lee appearing in Avengers: Endgame, and having that be his last on-screen appearance.
That movie really does feel like the culmination to everything that began when Nick Fury (Samuel L. Jackson) stepped out of the shadows to discuss The Avengers Initiative with Tony Stark (Robert Downey Jr.).