You mean improve our league position, improve our style of football, blood youngsters. That kind of thing?
Well, for a start Warburton left us in a worse league position. The only season in which our league position was confirmed under him, we finished 21st when we had been about 19th when he inherited the side.
League position when he was sacked is largely irrelevant, as you cannot prove that it was going to continue improvement, especially as we were falling like a stone. By that token, Karanka has also improved our league position from 21st to 17th, which us confirmed rather than based on fantasy.
In terms of blooding youngsters, I'm struggling to remember how many debuts have been given out by Warburton? I can't find any from our own academy youngsters. He played Tyler a bit, persisted with McKay and gave a lot of game time to Everton's youngster. It's hard to say that he really improved Smith as a player, he has destroyed Clough's career and Worrall has been consistently part of one of the club's worst defences ever.
Style of football is utterly opinion. No matter how much you try to justify it by comparing it to something even less palatable, the football under Warbs was mostly boring, turgid rubbish. The newspaper that talked about our 'sterile possession' had it 100% correct. It was the football equivalent of spending all afternoon in a church. Perhaps you can tell yourself that you have experienced something righteous but it's still boring as shit