We have mixed surfaces here on the coast of Maine in the greater Portland area. There are some dirt roads 10 miles or so to the North and West that we can get to from our doorsteps. But there are a lot of multi use paths and trails nearby. And yes, we have some of those "sexy cottage roads" here, too.
The industry has really latched onto gravel as a new market segment, and is clearly differentiating this from the most recent definition of traditional road riding, but the reality for many if not most people is that we should be riding all-road bikes. The bike companies seem to be going after this segment now, too.
I think you really need to think about where you're actually going to ride your bike and choose the one that best fits that terrain. I need something that can handle dirt but still be fast on pavement.
For me, in my region, a good, fast 650B converted racing or sport touring bike can fill that need pretty well. That's why I picked up on 650B conversions years ago. Many of the older steel rim brake bikes will fit a 38mm 650B tire, and I had a few of these bikes. They're like a gateway drug - ride them and you might get hooked and want to go for the straight dope; a full-on randonneur or a modern high tech gravel bike. Or maybe some other kind of high-end lightweight 650B endurance bike.
The newer disc brake frames that will fit 650B wheels and 42mm slicks like a Panaracer Pari-Moto or Gravelking are great. It's relatively easy to find factory 27.5/650B wheels that will drop right into these bikes. With these wheels and tires the bike will handle paths and dirt roads while still being fast on the pavement. These bikes open up all kinds of new routes through areas that would be difficult to ride on narrow tires.