Maybe I'm a dinosaur pining for the days of Giggs and Beckham, or maybe I'm just frustrated at the continual ineffectiveness of United's inverted wingers, but when and why did this become so popular in football?
You might have to consider that you’re too much of a dinosaur if you don’t remember that the days you describe also include Wenger inverting wingers such as Pires, Ljungberg and Overmars. Even before the advance of 4-3-3 as a system.
Ultimately statistics indicated that controlling the central midfield and maintaining possession of the ball increases your chances of winning, hence most teams play with 3 CMs these days. 4-4-2 became obsolete because teams were chasing shadows in midfield, as we found out in our continental encounters in the 00s.
As a result of the 3 CMs tactic there is one less out and out striker, so lobing crosses for 1 striker to fight against 2 CBs is a fools game statistically. So wingers became inside forwards or inverted wingers either becoming a goal threat themselves or being more involved in ball circulation and playmaking. Or if you’re Messi, in both.
This 4-3-3 with inverted wingers might be less aesthetically pleasing to some, but it is undoubtedly more efficient for a results driven team, than 4-4-2 with natural wingers. And football is a results business.
PS. Pep is now onto the next evolution of this, with a CB stepping into midfield to become an extra CM (what Stones does). Effectively having 2 DMs, 2 B2B CMs and 2 wide playmakers. Thus absolutely dominating possession and strangling the opposition.