Highly debateable.
And if you attribute our failure this season mainly to him, you also have to give him the majority of the credit for what the team achieved the past 4 years. So he wouldn't be "cancer to the club" either.
Oh no, not at all. He's used the same "opportunity signing" tactics as before but there's a huge difference.
1. We had a great motivator in Conte. So even when things didn't go our way (Or did you really forget how many drawings and 1-0 matches we had) tactically, Conte managed to make things work psychologically. We don't have it anymore,
2. We were starting from scratch. We used 4-4-2 before then we brought Conte who was given plenty of "opportunity" players to work with. We finally decided to stick with 3-5-2 and that seemed to work with Pirlo being his best and dictating everything. That's great and all. But now this team wasn't being built from scratch, we ALREADY had a SUCCESSFUL formula that worked almost flawlessly, all we needed to do was to improve upon that. Again, we DID NOT need to go through all this "finding the right players for the right system" again, we were progressing amazingly well given where we came from.
Yet what did we do? The same Marotta opportunity signings from back in 11/12 taking us back to the drawing board and throwing away all the hard work. And people really shouldn't be expecting Allegri to pull a Conte, it simply won't happen. I give the majority of the credit then to Conte for his motivational skills, Pirlo for being the main point in everything we did for at least 2 seasons and the general grinta and right mentality that our players had, even though our team wasn't the most talented out there.