Doucoure is fulfilling a role that Beto isn't yet up to filling. Martinez teams never 'just passed it round at the back' but that was what did for him. That was his philosophy, very much the same way it is for De Zerbi. The Moyes team had a better balance to it, a better balance than Martinez could muster. When he tried to fill the team with players capable of his philosophy, rather than a hybrid, he blew it cause the balance went. If we brought De Zerbi, the exact same thing would happen and we'd collapse quicker than your argument, because for a few years at least, you'd be asking Tarkowski to be Stones and Patterson to be Trippier. Neither will ever be either.
Let's look at the weekend, when were we really troubled, like properly last gasp defending. Once? Twice? They passed the ball a lot, much of it at the back when we stood off. Played lots of goalkicks sideways. They played nice 1 touch football, played passes on the turn, but a well organised team can be drilled to stop that, se nearly did and we're shabite.
Exciting football for me is counter attack football, forward balls looking to split a defence, it may even be one pass into the middle and then forwards or out wide to get the ball into the middle for the striker or supporting midfielder.
Dyche isn't the perfect manager for a great Everton side, but he's OK for what we are now, and his style suits the players we have at our disposal. As for purchasing Beto, it's much more sensible to buy one player that suits a squad and existing style than it is to buy the 9 we'd likely need to change the style to what you like. We tried doing that, it's left us fighting relegation for the last two seasons.