Yeah, it is difficult to compare players across rather large swathes of time, in fact it's purely imaginary. To the point of beyond even futility, just silliness. The best way to imagine it, perhaps, on the purely hypothetical plane, is to imagine some time warp or whatnot, that you travel to in an Einstein spaceship, and there's a football field, and a stadium all ready and waiting, or a basketball court, or a soccer field, and both sets of players, even though the guys from a previous generation are still alive in the form of like, 60 year old men or something, and then they just square off, and you really don't know what would happen, one just assumes the more modern players would win. Jordan vs Lebron is the most frequent example of this sort of thought exercise, even though basketball hasn't really changed that much at all. And I don't see any reason why prime Lebron kicks prime Jordan's ass.
The big thing that stands out is just a higher skill level, simply from practicing more, and in soccer players just have more ball skill now. The bar is higher. Like if you took Maradona vs Messi, which is about as perfect a hypothetical matchup with a pretty wide gulf of time separating them, Maradona to me looks more naturally gifted with just some special god given talent more than Messi, but Messi is technically better. And while he's gifted too, he's a more a product of his circumstances and development, is what I might guess, but who the F knows. The entire ambient world you grew up in, even outside their respective training regimens and regimes, is simply different, in ways that are impossible to quantify, but do of course define you as a living person. So like you say, older players would need some time adjust to the more highly practiced modern players. But they're not genetically superior, not enough time passed for that. If of course, you could suspend the constraints of existential reality and do something like that.