Reads like a GOT Lukaku post from 2016/17, that.
I like Doucoure, personally. I think he's very good on his day and if he's driven/"hungry", he'll become one of our best players very quickly. At 27, he's probably not just rocking up for a final pay-cheque and it's good we're getting someone who knows the league and will probably "hit the ground running", so to speak.
There are two other main important factors for me in the midfielder, besides general footballing ability that I value in that i) he contributes a fair number of goals for a midfielder (he got 7 in the league in 17-18, when Watford were actually an ok side) and ii) he seems to have an excellent record with injuries, being a near ever-present for Watford for the last 3 years. Obviously that means little when it comes to Everton (see Gbamin, JP), but it's something that'd be near the top of my list of priorities in signing players these days.
So he's premier league "proven", experienced, has a great injury record, scrores goals and is in his "prime". For a side with an abysmal midfield that is desperately short of goals and needs results quickly, I could think of worse additions. Not that there aren't possibly better options, but I really wouldn't be against this signing at all.