It's not a remotely outrageous deal. If the Yankees believe he's worth the QO...they've committed essentially the same amount per year, over two years instead of one. They're taking on the risk of decline, but only over one additional season. If Rizzo's play holds up, they have the third-year option.
For an older player, it's a sensible approach by the Yankees. If he's currently worth $19.5 million (and offering the QO says the Yankees believe he is), then a two-year deal at $20 million per...is taking on the risk of decline, but only for one additional season. In exchange, they acquire the option to his services in year three, at a lower rate, if the decline doesn't happen (or is minimal). But there's no long-term exposure, unless Rizzo falls off a cliff in 2023. If the Yankees thought that was much of a risk, they wouldn't have made the QO.
For Rizzo...he's locked in a second year at a good salary - a hedge against decline. He's staying in New York. (Whatever you think about New York vs. other cities, relocating is a pain.) If his game does fall off a cliff, he's locked in a very nice soft landing with a $6 million buyout.