In fact, it is incredible that the dominance of the "big three" in men's tennis has lasted so long and that together they have won as many as 64 GS. Something like this will probably never happen again in the history of tennis or any other sport, that three of the best athletes compete at the same time, against each other.
I had much higher expectations from Medvedev, Zverev, Tsitsipas, Thiem and other young hopefuls, but even though some of them managed to win some GS, they still could not break the dominance of the big three.
Whether Alcaraz can do that this year and end their dominance, if fit and healthy, remains to be seen.
I agree, every era will have one or max 2 superstars but having 3 such a great players at the same time is something that we will not ever see again anymore I think. They dominated more than 10-15 years and now we have a lot of young talented players but no one really stands out. Alcaraz is probably the one that can win the most grand slam titles of them all but I doubt he will able to dominate the field in the same way as Federer, Nadal and Djokovic did.