Not just ex-players a lot of the time, pick any player with a thread and it can apply to them.
Young player or a new signing to the PL does well for a few games - thread started. Forgotten about, sometimes for months or years until they hit some form again.
There's the odd opposite example like you say. Lukaku springs to mind, people only wanting to talk about him after a stinker.
Moyes manager discussion only when he's on a bad run.
There might be some online football spaces where there's in depth discussion about all kinds of performances for all players but the Caf isn't it and it's going to be very rare. It's human nature, people only becoming aware of something because it's grabbed the headlines and probably didn't even watch the game. Not everyone sitting there watching every minute of every game.
The Tyler Dibling thread wasn't bumped this weekend after presumably a quiet game as a random example. Nobody really giving a shit to learn exactly how he played, the ins and outs of his game, anything he did well, anything he did bad and his development apart from Southampton fans on their forum.