With Khachanov winning his first Master's tournament, there are now 2 under 25 players who have won Master's; Zverev being the other (he has won 3).
Is a generational change happening and just skipping over the aged 25-30 crowd?  Cilic and Del Potro have won slams, but they have not shown the consistent excellence that Federer/Nadal/Djokovic/Murray have.  Despite a lot of hype for Thiem as the next big thing on clay courts, he hasn't won a Master's on the surface, but he did make the final of the French Open.
I've thought that the commentators have been a little harsh on Zverev's slam results, maybe with Khachanov being more prominent, it will take off some of the pressure.