We call this efficiency.

Ferran Torres is definitely way better than Rashford, he's just underrated, he even score more goals than Mikel Oyarzabal for Spain.
Torres score 2 goals from 3 matches, Rashford contribute zero goal and zero assist from 3 matches, with his salary, Barcelona can find better player compared to Rashford.
Moving to Turkish is a good move, probably he can play with Onana in Trabzonspor or join Fenerbahce, Mourinho will able to make him discipline.
Right now Marcus Rashford is not doing anything good like his didn't even make any sense in Barca jersey, and because of this Hansi Flick warned him that if he didn't improve his performance level then he would be sent to the bench for the rest of the season. Barcelona signed him to boost team performance, but unfortunately Marcus Rashford has not shown any improvement. So maybe Barcelona will just keep him until the loan ends and then send him back to Manchester United.
Marcus Rashford needs to improve his performance because Barcelona wants a player who can contribute to the team in a better way, and if he doesn't complete this criterion, they will kick him out of the team.