of course he is not and never will be fernandinho, but fernandinho wasn't perfect either.
Rodri has specific skills - where he is world class.
Pass Accuracy (long ball / small passes) -> Best
Dribble, first touch and ball control (pep`s beloved rondo skills) -> Best (better than fernandinho)
Physicality (he wins 50/50 battles and headers and etc) -> Best
Intelligence (finished college, reads game and is a good guy in overall) -> Best
The only thing he isn't good at is his pace and that's something busquets and matic and other midfielders similar to him lack.
So team needs to adapt, because we won't get someone like him, you can't find decent DM in the market right now..
How this can be done:
1) centre backs and midfielders press aggressively and help him to defend
2) certain attackers stop loosing ball in the situations, where opponent has good opportunity to start counter attack and rodri / team isn't able to re-organize. I would love sterling to improve his first touch. There are situations during the game when he looses the ball due to reason that his first touch is awful and isn't able to distribute passes with one touch. (for example - gabriel jesus is best in this component.. one touch passes is something, that makes Jesus irreplaceable)
Because otherwise when it's somehow predictable that team or attacker looses ball - rodri knows where to arrive and stand, so that he can block any attempt of counter attack..
That's the only detail team needs to improve, so that Rodri`s flows are covered and in addition to that - we can use his passing and other abilities to control the game better...