Ahh, good old Slam Absolutism...Nadalfan2013, is that you?
Unfortunately tennis isn't only about the Slams.
As for Rafa vs Carlos, it reminds me of the question people ask in baseball: Some variation of, would you rather have a pitcher with a 3.00 ERA in 200 innings or 2.50 ERA in 150 innings? Not sure there's a great answer for that.
Meaning, I do agree that if we're looking at who has been the "pound for pound" best player, Rafa edges out Alcaraz. By that same logic, Roger was the best player in 2017, not Rafa; and probably Novak over Andy in 2016. I'm sure we could find other instances.
But in the end, the world number one is based on a formula that also recognizes consistency and the ability to stay healthy as part of it - as it should.