I'm on a gen 2 Santa Cruz Stigmata I bought on closeout at the LBS. It's the most comfortable bike I've ever owned and its fast. I've looked at the brand new SC Stigmata that came out last month that fits 700x45c/650b x 2.1 combos. the Rival 1 build spec is $3599 and well worth it in my opinion. I would seriously consider this bike if were shopping still.
As far as boutique brands, a company in my home state of Arkansas called Allied Cycle Works is making some gorgeous bicycles and have 2 allroad/gravel models.
https://alliedcycleworks.com/ They do range in that $5k-10k range but for a custom bike 100% made in the USA, I drool every time I see even a picture of one. Their bikes I've seen at the LBS are almost too good looking to ride! I WILL own one one day.
https://alliedcycleworks.com/pages/allied-alfa-allroad 700 x 23-38 tires
https://alliedcycleworks.com/pages/allied-able 700 x 43-650b x 47