Icheb was most definately in endgame. He beats Tuvok at a game of Kal-Toh, which is when Tuvok figures out his condition is getting worse, which ties into the earlier scenes of him being mentally incapacitated.
As for saying goodbye to Neelix, it was never established that Neelix and Icheb had much of a relationship, if at all. So it would make sense if his farewell was not focused on.
I loved Icheb. I think he's cute in a really twistedly nerdy way (even though, yes, his clothes are horrible...and he has a double-chin thing going on). I think his character was hinted to have more depth and complexity than explored -which is perfectly fine for any supporting character. This is especially evident in Child's Play and the episode where he risks his life to save 7 of 9. And in Q2, where he finally is with someone his own age and has to fight peer pressure.
Icheb > Wesley