I hear you and don't disagree with your caution, but I see a mentality in Rune that was (is) lacking in Tsitsipas and Zverev. He seems to have "It" - be it a cocky arrogance that is backed up, a championship mentality, etc.
I see Sinner on a lower level than Alcaraz and Rune. As I said several months ago, he appears a bit fragile - and his frequent injuries seem to support that notion. I really like his calm demeanor on court, and in some sense he's more of a Child of Federer (at least in that regard), and I do think he'll be an eventual Slam winner, but ten years from now, I see there being a significant gap between Alcaraz/Rune and Sinner, in terms of Slams and such.
Or to offer a fearless prediction, if I were to guess right now at eventual Slams won: Alcaraz 10, Rune 7, Sinner 3. All could win more or less, but that's what my gut tells me. I reserve the right to change that prediction!