Ronaldo is not a problem to Manchester United, they don't really depend on him, so if he likes he stays or leave Manchester United won't be affected. Manchester United are doing well in performance presently not even because of Ronaldo's. Ronaldo has only score 1 goal for Manchester United in the Europa League and has not score any goal in the premier league this season.
Its a problem in fact they still need to pay him hefty sum of money either if he is playing or on the bench. Basically Ronaldo is not the type of player that would be comfortable sitting on the bench so Ten Hag is left with the option of subbing him in regularly even if it isnt needed to so there is an extra slot of substitutions being wasted just to let him play even when the club doesnt need him