Well, let's take a look at this!
They wrote off Tasha Yar because the actress wanted to quit. I didn't like that they killed off Yar but in this case it was clear that the actress wanted out and both those in charge and the actress came out with clear statements about it at that time. However, it was a mistake to kill off Yar since the actress did change her mind and wanted to come back, therefore we had to stand "Yesterday's Enterprise" and the silly Sela plot.
Beverly Crusher was dumped after one season which was as stupid as when they dumped Kes. However, in the Crusher case those in charge did realise their mistake and brought back Crusher aftere one years absence. All the time after Kes was dumped, I wished that they would realize their mistake and bring her back too but.............
Wesley Crusher was dumped after three seasons. However, they had him as a recurring character for the rest of the series and even if I don't like how they messed him up in "Journey's End" when he left with that sleazy Traveler, they didn't ruin him as they did with Kes in that insulting season 6 episode.
So except maybe for Yar, TNG never reached the unnesessary character destruction we had to stand in Voyager. And yes, I can watch all seasons of TNG But I must state that each season of TNG had more bum episodes than season 1, season 2 and season 3 of Voyager had.
As for Crusher, I think they wasted a golden opportunity there. They should have ahd him continue as a Starfleet officer and then the next series could have been about Wesley as a captain of his own ship. Instead they brought us "Enterprise" and now "Discovery", another pre-TOS series.