The Kane comparison doesn't really make any sense. He is playing great because of Pochettino's setup. They are playing great stuff on their day and Kane is great of course. That our goalkeeper is our best player and still need to do tons of saves all the time doesn't speak four our team, it even makes you question our defence, which really isn't that good.
Sarri needed a bit of time to get to the top flight, does it matter? One he arrived there, he did a great job at Empoli and Napoli now. At the end of the year he might have won Serie A. And I know that Jardim proved he can be very pragmatic too, did a great job at Sporting and Monaco nevertheless. They are managers on the up atm, you can go for Allegri in the summer too. At the end looking at records from the last decade brought us to van Gaal and maybe Jose, but they might have their best days behind them and it doesn't matter today.
In the end we need to look at someone else if it isn't working. To just put the head in the sand and ignore big problems will just lead uns into a bigger crisis. Jose is a short-term manager, he never struggled so much for having an huge impact on his team and he never improved a team further in his third year and more, so I don't think it's likely those things happen here.