Murray played in one of the toughest eras of all time so I think the slam count is a little skewed as a result. I can't see Alcaraz being able to navigate a prime Big 3 to 4 slams by age 21.
In any event, he has major holes in his game. The serve is an unreliable weapon, his ground game is highly erratic and I question his Tennis IQ. He's a magical player who is an elite shot maker and an elite mover but he lacks some of the basics in his game/gamesmanship that the true greatest players had. His talent and physicality is up there with the best of all time but his mental awareness seems to be lacking and I'm not sure that'll ever be corrected.
This was just a very disappointing effort from him, he seemed way too passive as if he was in awe of Djokovic and I don't seem to recall younger Carlos being that way. He seemed more fearless before, now he seems hesitant and unsure.
Not to take away from Djokovic who can still turn it up to a high level but Alcaraz shouldn't be losing this match in his now prime.