I wouldn't put it exactly like that because there's more to what constitutes a top-class midfielder nowadays, and the traditional binary division between defensive and attacking midfielders (which, to no surprise, is still one of the Caf's favourite pastimes) doesn't seem able to capture all the nuances of the varied roles at the centre of the park. Because it's the "roles" that matter, not the "positions".
Nevertheless, the gist of the OP is correct. I'd argue that what we're witnessing (and it has actually spawned some decent discussions in several players' threads) is the death of the "hard-man" in the midfield. Control and domination. Control the ball with good possession and control the pitch with good movement off the ball. One will argue that this has always been the case. What has changed is that, for a good 15 years now, more and more teams subscribe to the trend (advocated by both Pep and Klopp) that domination, no matter the philosophy, should be achieved in the opposition third. This has ultimately led to a new crop of players with a wide set of skills who are being preferred for the midfield roles.
Mount is a good signing for United. If we take De Jong as the model for what ETH wanted for that LCM role, it's a risky move. He can press, he can pass and he can deliver a killer pass from the half-spaces. Plus, he's an adequate ball-carrier and he possesses the skill-set to wriggle out of a tight spot without constantly losing the ball, which is a rarity in this United side.
If there's one difference between United and what the rest of the competition is trying to implement (and we still have to wait and see how the team will play next season), one could argue that the others get upgrades to enhance the way their midfield as a whole while Mount seems like an attempt to strike the right balance by adding and subtracting qualities. On the ball, he can be the yin to the yang that Bruno and Rashford often thrive in.
For what it's worth, i think Arteta's plan (on paper) is more courageous in terms of high-risk, high reward. But they have last season's foundations to build on, and Rice is an absolutely massive signing for them. It's also a move that fully agrees with what the OP is suggesting. Energy and endless running (as the only qualities in a midfielder) aren't prerequisites any more to balance out the more adventurous positioning that aims to dominate the spaces between the lines in the opponent's half. These things can be achieved via possession and off the ball movement. Possession, not as a means to always seek out the final pass so much, but more as the ability (Pep often puts in nicely) to "see the space". And off the ball movement not as a tool to get on the ball and become a hero, but to open up more options and help the team's shape maintain its balance. Possession and movement off the ball to increase the threat without unsettling the team's equilibrium. This is the endgame at the top of the pyramid nowadays.