You're overestimating van Dijk's influence which is quite an impressive feat to achieve, considering how truly influential he was for Liverpool.
Their midfield was what helped with the fullbacks issue first and foremost — it was an extremely worksmanship-like unit with Fabinho, Henderson (whose role of covering for Trent would be the most obvious example of this support) and Wijnaldum. That system started to struggle when Klopp introduced Thiago — individually a superior player to any of the previous trio but someone who is more focused on keeping possession and leading the game instead of covering for overlapping fullbacks. Van Dijk's pace and positional play also helped them out a lot but he wasn't the only thing keeping that team together — which is evident by how poor they were at times lately even with him recovered from his injuries. There's Alisson, there's Henderson, there's team cohesiveness and an insane level of fitness — every part of it played a huge role. Would it've fallen apart without van Dijk? Yes. But it would've fallen apart without other crucial details too, just like it did.
And as someone who've seen a lot of other GOAT-level defenders, he doesn't really stand out in comparisons with them. He's probably the best defender of the past 10-15 years, at least in terms of his peak, but that's about it. And Baresi & Beckenbauer were simply better.