Rubio's Gen-X (he was born in 1971), but I get your point. There will be a period where Gen-X has to run things, but it's going to be extremely brief due to the Boomers hanging on until they literally expire, and the Millennials chomping at the bit to jump into their spots due to that particular generational rivalry. Gen-X just doesn't have that same political drive.
With Gen-X just starting to enter into their 60s now and retirement on the horizon, I suspect a lot of politicians from that generation are going to essentially term-limit themselves and let the Millennials run things while they sit on the porch. Gen-X's general instinct in their adulthood has mostly been to keep a relatively low profile and do the grind, not drive the cultural or political zeitgeist. Even older ones with large public profiles like Newsom and Pritzker give off an aura of low energy and just use their money to make up for their overall lack of charisma.