Fellaini is better than every midfielder we have bar Pogba, maaaaybe McTominay at a stretch. Same applies for Herrera, fact is the club and manager couldn't be arsed to replace either because they thought the CMs were dispensable. Lukaku with all his flaws is still better than any CF we have in the club at the moment. Smalling is better than every CB at the club bar Maguire. So yes, he's got rid of many useful players who could've helped us this season. They were better than their existing counterparts and were never replaced.
Just because a player is getting abuse doesn't mean they deserve it, it applied for Fellaini and Lukaku. It applies for Young too, you're digging yourself into a hole by going down the route of whataboutism.