I'd argue the exact opposite, since we have lots of people asking for us to pay 80-100M for Rice, and almost no one who says Matic is a good midfielder anymore. So I would say Rice is overrated and Matic is underrated. Anyway...
We play the McFred midfield because they are our only pure CMs, and our only partnership which is somewhat succesful. VdB and Pogba are not really CMs, and Matic is over the hill. Neither McT or Fred are "shielding the backfour" type players, they are box to box ball winners like say Fletcher or Marchisio. We had a midfield of Fletcher-Scholes, and that didnt need a "shield" either. Kante is also such a box to box ball winner who doesnt "shield the defence".
I can turn around what you said, and say the same thing that "we play McFred because we dont have an elite DLP". To think of midfield as one player doing all the attacking, and one player doing all the defending is overly-simplistic. If that was so box to box players wouldnt exist. Truth is McFred are limited players, but they are the most natural ones we have right now. You can pair Pogba with someone who can "shield the back 4 on their own" and it would still not be a press resistant midfield, unless that midfielder is a good passer. Pogba is not a DLP, he cannot control games.
If we pair McT/Fred with Thiago/Jorginho, I can guarantee that would be a great midfield. You have the legs and ball winning ability of Fred, with the passing and positional ability of Jorginho.