I have seen a couple of Ribble CGR bikes in gravel races, they look great and thats about everything I have for direct experience.
When I was looking at a new gravel frame a couple years ago, I considered a Ribble CGR but nixed it off the list because sizing didnt fit me. Everything else though?- the frame was on point and for a great price. If they had one in my stack/reach, I would have probably pulled the trigger. In the end, I bought a frame from a different British brand.

I have purchased a lot from components from Ribble over the years- its a large and established retailer and service was quick.


Personally, I would not hesitate to buy a bike from Ribble. If you know your ideal geometry and the Ribble frame works, then yeah go for it. I have never purchased a bike frame in person- always bought them online and also built one. Knowing the stack, reach, bb drop, trail, and chainstay length will give you basically everything you need to determine if a bike will fit and feel the way you want.
Ribble's house brand bikes are very well established. This isnt something new for them- they have their own designs and from what I have read they also have contracted with manufacturers to tweak established molds. Ribble created what they claim is the fastest aero road bike in the world- the Ultra SL R Aero. I mention this to show they apparently put some actual effort into design.