I would repeat that that Barca was one of the best in the world because of Messi and also that La Liga was the best league during that period. One can also ask questions such as "I wonder how Ronaldo would perform without SAF at United with other stars / Modric-Kroos at Real" etc. You also seem to struggle to understand that La Liga top players do not care about PL, it is not their dream to go to Manchester or Liverpool to prove themselves to Ronaldo fans
They are playing for Real and Barca, the best teams in the world in the best league in the world. It is Ronald fans' own standard measure to ask such silly things like Messi did not play in PL against PL teams, so that does not count which is absurd. Xavi, Iniesta also only played for that Barca as well, so should we discount their performances against PL teams, too?
Messi with Argentina also won multiple MVPs at Copa, WC, Olympics, U-20 WC, basically whichever tournament he competed in, he won the best player award since he was like 18, what else do you want him to do at the NT level to be satisfied? Do you hold Ronaldo to the same standards? How do you view the fact that Ronaldo could not win even a single best player award in an international tournament (4 WCs + 5 Euros) something that Forlan with Uruguay, Zagorakis with Greece, Schmeichel with Denmark, Modric with Croatia were able to do? Also, how do you explain that trash Portugal team managed to beat France in the EC finals without Ronaldo?
I used "limited" in the areas of creativity, technique, dribbling etc. He definitely became a more prolific goal scorer due to transforming into a striker/poacher, what's surprising about that? Ronaldo before that transformation was a more creative, versatile player while winning less. He basically failed to replicate his playing style at United at other teams such as Real (with the exception of the first couple of years) or Juve.
It might be hard for Ronaldo fans to understand, but most non-Ronaldo fans would find his United version his best version not the poacher version which is a stats machine. Imagine Maradona/Messi becoming a poacher to maximize their goal scoring stats, most Maradona/Messi fans would not appreciate that. Both at Real and Juve, the whole team was designed to feed Ronaldo a the expense of other strikers such as Benzema, Dybala etc. meaning he would get a few chances every game anyway, he did not have any responsibility to run the game, create chances, dribble past players etc.