While I agree with the sentiment of the OP, that we could do with upgrading our playmakers from Herrera, Mata, Rooney etc to players of the quality of Isco, we have bigger, more basic issues to resolve with regards to creativity IMO.
Liverpool are looking a pretty creative team these days, for example. Why is that? They have Coutinho who is very good, and Firminho appears quite good, but the rest of the squad is not particularly littered with creativity. The thing they have started to get right, is that they are creating and attacking as a team. They're not completely reliant on individuals performing an isolated moment of individual class all the time. Do they rely on it sometimes? Of course they do. Coutinho ripping Varela apart yesterday was an individual moment of class. But as a team, they create, using intelligence, cohesiveness and fluidity when on the ball.
What we do, as opposed to that, is give the ball to a few selected players who are deemed to "have skill" and hope they do something interesting.
There's a fundamental difference, whether intended or not. It makes our creativity a much bigger effort and demands a lot more out of our creative talents.
Spurs are an even better example for the OP (and others). Who in their team has a huge deal of guile and creativity? I mean, Lamela has a bit of it but is by no means top class. Eriksson is quite good. Deli Ali? Kane? They're no Isco level players either. But they create plenty of chances through being a good TEAM.
So the crucial step is to make yourself a proper team that is capable of attacking as a cohesive unit, and then adding worldie talents will only further elevate you. But continue being disjoint and you'll have to spend 200 million to achieve what 75 million could have.