Pumps dont nessesarily mean you're gaining size. Sure there great that motivation, and me gustas in the mirror, but compounds are the best because they activate more CNS, thus more testosterone production. Don't stop doing isolations though, but do them at the end rather. I find isolations are are great for touching up on weak areas.
FYI the reason why isolations produce better pumps is because the blood is rushing to the isolated muscle because that's all that's being worked in that movement
