Back in season 3 and 4 top lane was a true island. Mid and bot lane had all the fighting, so top laners were able to duke it out for a good 15-20 minutes with even minimal jungle interference. The isolation was part of the appeal.
As it stands now if you isolate yourself up there you are just throwing away whatever lead you're gathering. You are forced to teleport and roam to effect the other lanes, because your lane simply will not decide the game. Even Nasus, who in the past could farm for 20 minutes and then show up and one shot the enemy ADC out of nowhere, has trouble if his bot lane loses, because if he doesn't assist the other lanes before 20 minutes the other lanes will show up top lane and ruin his day.
As a top lane main the isolation is a good thing, but the level of impact you are responsible for is getting harder and harder to pull off.