That is the only argument that i recognize that the game was harder, it was indeed full of "vinnie Jones" thus would be very hard in that sense, but as far the game itself , it evolved so much. I have zero doubts that a fit Robben would be the best player of 80s or the very least top 3. Not even bring Ronaldo and Messi to the converstation, i think is preposterous, to compare them to old players in any sense.
Could do the same for strikers, a Lewa, Ibra, Suarez, Benzema, they would be the best strikers in the 80s minus maybe Van Basten and is a big maybe,
I think this is offtopic, so it's my last post on this: You can't just assume a modern player would be just as good if he played in the 80s or even earlier. Today's players have huge staffs that are eager to make it as easy as possible for them to focus on football. They have mich bigger coaching teams that have much more knowledge about health, fitness, cognition etc. Also scouting teams that help them identify the weaknesses of opponents, performance diagnostics, video analyses and so forth. They earn so much money that they can buy everything tgey want, employ personal cooks and nutrition experts, have the best doctors possible, can sleep between training sessions, are sought after by physios whenever they need them, ... Pele, di Stefano and so on were pioneers. And relatively speaking, they were farther ahead of their journeyman than Robben. Especially Pele was ridiculously far ahead of everyone else in the game.
There's this saying that goes "if I look tall, it's only because I'm standing on the shoulders of giants" or something like that.