See I like solid,as in robust, but I don't want heavy.
What wears out.... bearings, drivetrain, brakes, shifters, seals,rims, discs, and then eventually, when pushed hard enough often enough, the frame. Though that tends to be catastrophic failure mode time, rather than wear and I've only done it two ir three times in 20 years, once in a race and once on an alp. That said my old Rockhopper (of which the frame is the only original component) still serves its new owner on tarmac and my pub singlespeed is a 94 Kona frame.
"Better" stuff just works better, and ime, lasts a bit longer. You get lighter stuff which builds into a lighter bike without compromising strength or durability and that makes for a 'nicer' experience.
I was, frankly gobspmacked by how much mtbs have come on in the last 10 years.