Exactly. This article sums it up well -
https://statsbomb.com/2019/01/the-rise-of-press-resistant-midfielders/
Press-resistant central players are becoming irreplaceable given current football trends of high pressing / smart pressing in high-intensity zones. Teams are realizing this, too, which is why they're in such high demand - with Frenkie De Jong and Tanguy NDombele both examples of this skillset. At their most basic, they create space for others - at their most devastating, they single-handedly decide games and entire seasons with marauding runs through midfield, opponents bouncing off them at will.
The article being headlined with a picture of Mousa isn't an accident, either - he was basically the poster boy for powerful, unstoppable press resistance, the first of a new mould of central midfielders that could counteract the gegenpressing in vogue at the time. In many ways, Poch's usage of Dembele created the tactical demand for that style of player across the continent, and is the reason why Poch loved him so much. In many ways, Mousa was a first.
No doubt the entire team has suffered from Mousa's decline and subsequent sale. Attackers have had less space to operate in, and have had to turn the ball over quicker. Dispossessions have gone up, meaning the team has had to run more to recover the ball. Defenders don't have an easy out ball ,and opponents have more players available to spring on counters.
We miss Mousa, or someone like him. Surprisingly enough, Sissoko has fulfilled many aspects of that function this season - his passing is very questionable, but in terms of pace ,strength, dribbling skills and workrate, he's pretty much been the surprise package of the season in terms of replacing Dembele.
But he's had to put in multiple shifts as a defensive midfielder, negating most aspects of this skill. And of course, we might not have him for the run-in.
Whatever happens, this summer we will need to decide what we do about that central midfield position. Do we settle on Sissoko as a DM? In that case, we need another press-resistant central midfielder to take up the slack on the other side.
Or, alternately...do we get Sissoko to play more of a ball-carrier role next season, and sign a new DM to replace him? If so, some interesting combinations emerge.
The most interesting would be to play a deep-lying regista alongside Sissoko - to provide a new vector to threaten the opponent by having that player pick up the ball in deep areas and immediately spring counters with long balls. It would also be the most balanced solution, and would allow for a team brimming with menace.
Another option would be to do away with the need for a 'pure' DM, and sign another ball-carrying player (Tanguy NDombele) to sit at the base of midfield. Then, Sissoko and NDombele could take turns alternating runs forward, and it would allow for plenty of cover for that role should one get injured.
Either way, this CL run has been an absolute blessing, because it allows us to bring in that calibre of player this summer, provided we get CL. And that, in turn, will free up Eriksen, Alli, Son and Kane to a huge extent next season - if we can pull it off.