Well, it's better than the colossal flop that was the Pixel 4/4 XL. A phone so bad Google had to roll back features they introduced to the Pixel lineup and were saying at P4's reveal that they'd be features that would be part of the Pixel hardware in future. Oops, the very next year they get scrapped. Android Central called the phone a flop, MKBHD called it the bust of the year -> so Google going in a different direction this year is a smart move.
It's not a high-end flagship. Maybe Google have woken up and realised consumers don't want to pay more for less, so they've dropped out of the high-end market. If you go just on specs, yes there are better products out on the market at that price point, like the Galaxy S20 Fan Edition. But on a whole, the Pixel 5 looks like a decent enough phone for a somewhat reasonable price.
Is it underwhelming? Well it doesn't do anything to push the needle on phones, so I guess that could be underwhelming, but then again it's not a a $900+ phone, so you can't expect some bleeding edge features.
OP if you're not impressed, then don't part with your money. Only buy a product that you're happy with. Yeah your Pixel 3XL can get upgraded, but if the Pixel 5 or any other phone on the market isn't compelling you, then keep the money and spend it on a phone that you really want imo. The Pixel 3XL will still get the next android update and security patches, so it should be fine for another year.