I too am a former MTB bike rider and racer looking to into a modern bike. Not sure this will answer your question directly, but I can share some insights from my own recent research. For background, my current bike is a 24-year-old Jamis steel hardtail with a very aggressive geometry that I selected specifically (at the time) for XC racing. It has a Shimano XT drive train and a mid-level Manitou fork with seals that are long dead.
When I was still racing back in my late teens/early 20s there were basically two types of MTN bikes: XC and downhill (there were cyclocross bikes as well, but they were never single-track capable IMHO)
Now it seems like there are more sub-divisions of mountain bikes, in order from most aggressive geometry to most slack:
I'm no longer interested in the ultra-lightweight and super nimble aspects of an XC bike because I no longer race, so I've been looking primarily at Trail bikes because they are available in hardtail (to date I have not seen any hardtail classified as an Enduro, but that doesn't mean they don't exist) and have a more slack riding position.
When I bought my Jamis I went with steel because it was slightly more compliant ride, and it was overall cheaper. Carbon at the time was way out of budget (and frankly, still is). That seems to be reversed now - steel frames are still available, but seem to be more expensive and AL seems to be the go-to for most hardtails in the 1500€ - 2700€ ($1700 - $3000 USD) range. From reviews I've seen online (written and video) the geometries and construction techniques for AL seem to have dialed out the harshness common to AL frames in the late 90s. Of course, I suppose I'll find out if that's the case once I get out on the trail.
The one thing I've read consistently in the reviews (and was true when I was shopping for a bike 24 years ago) was to swing a leg over a bike you're interested in and make sure the riding geometry will work for you. No combination of frame material or group set will make up for picking a geometry that sucks for your riding style.
So, all that said, I've narrowed my selection down to the following. They're primarily mass produced but only because the boutique hand-built frames are out of my price range. Also, in my part of the world (central U.S.) it's almost impossible to find a hardtail Trail bike to buy much less rent or try out, so I haven't bought anything yet - I'm waiting until I can get a chance to try these out before a make a decision, and the supply chain issues seem to be double for the boutique small batch builders. Anyway:
- Trek Roscoe
- Cannondale Trail
- Specialized Fuse
- Salsa Timberjack
You're obviously in Europe so I can't speak to the availability of these bikes, although I know the Roscoe is available at least in the U.K. because they get a color option I want that is not available in the U.S.