Simply signing a “world class” midfielder will not remedy the multi-dimensional and long-standing issues we face, I'm afraid. Sure, some of the concerns will be alleviated with the injection of markedly better quality, but many others will remain if we do not have a coherent framework in mind. What even is a world class midfielder, and will this particular individual really address the crux of the problem, regardless of profile? We have signed players (not just midfielders) who were considered world class, or close to it, by lots of observers, but most of them did not pan out for various footballing and non-footballing reasons: Mata, Di María, Pogba, Sánchez, Sancho and so forth. Now, we should definitely not give up on signing top, top players and things could (and probably will) be different under ten Hag (vis-à-vis Moyes, van Gaal, Mourinho and Solskjær), but our recent history (as regards improper, neverending and ridiculously expensive midfield retooling) points to suboptimal analyses, prioritization and recruitment, and perhaps the club needs to take a step back, revisit the principles that have led us astray and consider the broader picture?
Before we try to move forward and make massive investments, we need to figure out what we really need from the midfield department in exceedingly specific terms (and with regard to challenging Manchester City on a consistent basis on all fronts, because they are not going away for the foreseeable future and will continue to set the benchmark, as the team to beat in English football). At least try to build a technically accomplished, dynamic, press-resistant and tactically astute collective that can play on the front foot against the best teams (with qualities that complement each other to engineer a whole which is greater than sum of parts). Suggestions of us piling up on a myriad workhorses and tenacious role players are gob-smacking; this is Manchester United, working hard and putting in a tactical shift is fine but in many ways the absolute minimum in terms of requirements, and we should seek to dazzle and dominate the heart of the pitch as well as the crucial half-spaces (particularly on the ball), not give up and resort to reactive football to contain our superiors (while attempting to strike back during transitions).
Acquiring as many evasive, quick-thinking, courageous and purposeful ball-carriers as possible (who can also retain possession in condensed zones), for every department, is very much the need of the hour — that releases pressure, creates pockets of space, makes the opposition work harder (especially if you vary your approach with routine pass-and-move combinations), and so on and so forth. There are times when out-of-his-diapers Alejandro Garnacho is our only credible ball-carrying threat on the pitch (which makes it easier for the opposition to contain us). Like, what gives, who are our reliably strong and technically superb dribblers? Looking at some of the playmaking ball-carriers at Manchester City (Grealish, Silva, Foden) or even Arsenal (Ødegaard, Saka, Martinelli), we don't measure up (and that needs fixing). Not even thinking about someone who can control the game, at this moment — players who can do that are rare (we should be deliberate and methodical with our move, in the contemporary game you need someone who can pass well on all three levels and also effortlessly bypass rigorous pressing with deft maneuvers), and we also need to sort out other midfield-related issues first (as long as the appropriate groundwork is not laid, even an accomplished architect will be stifled and start underperforming).