Like Casemiro, he improves players around him, although having Joelinton converted into another Mousa Dembele through coaching/repositioning helps too. With those two in particular there's a combination of physicality and passing competency we don't have without Cas (plus Eriksen providing passing outlet and control)in the team. Newcastle already dominated the cnetre of the park in the League cup final, so it was unsurprising that things were even worse on Sunday.
Bruno G is pretty high-grade but there are plenty of other players who broadly meet the criteria of strength, agility to break and beat the press, and who can still pass (and show to recycle under pressure) 3-4x better than McT, all of which we should be looking for as profile for at least one squad midfielder in addition to a long-term Eriksen replacement. Without that, particularly with Casemiro potentially being out next time we play a team like this, similar issues are just going to keep occurring.