I'm not sure twenty years later is "suddenly."
I'm perfectly happy to assume that they broke up amicably sometime over the last two decades, especially since they were never all that compelling a couple in the first place. I suspect that the number of viewers who were actually invested in that particular relationship number in the dozens at most.
There are dozens of us, dozens!

In all seriousness, though - it's less "this" particular relationship, than not really caring about what PIC does with any of our familiar characters in general, because everything is so absolutely over-the-top extreme anyway.
Riker & Troi having lost a child would have taken an extreme punch on TNG or the movies. Here, that makes them some of the "happy" people, who got better off. Same for Seven - it's not so much that I was a fan of her and Chakotay. It just seems odd to have her, 20 years later, be on one merciless revenge-plot after another, on the emotional brink like the Punisher, after whe spend 4 years before with her discovering what it is to be human, in steps like "talk about your feelings", "what is friendship", "go on dates" and "learn what individuality is".