I happen to think a reverse of this statement holds just as much truth: I don't believe strong CBs/midfield will make a big enough difference in Amorim’s system without having some creativity and penetration in the wide areas via proper WBs.
One of our most obvious deficiencies right now is our inability to stretch teams, work openings and create chances. Even if we get the personnel to control games better, we’re still going to lose games and drop points if we can’t figure out how to score a lot more goals than we do currently. And the WBs seem key to that happening in Amorim’s system.
When you then consider the wide players that will likely never play for us again (Rashford, Sancho, Anthony, Shaw), adding some more quality on the flanks seems absolutely imperative to me. Whilst I agree that we desperately need reinforcements in the middle, especially a mobile MF who can control the tempo and pass through the lines, I just think our needs out wide are just as glaring if Amorim is to be a success.