My top 5 mtb inventions:
Enduro FS bikes - it's an enabler that allowed more access to terrain that once caused a lot of anxiety, especially regarding risk of injury and risk of getting stranded by mechanical failure. It allowed me to go the pace I desired, one that I'd describe as being more free and flowing. The dreaded squat when climbing a long travel bike has been nicely addressed as of late (through geo)
Class 1 pedal assist motor (Shimano STEPS) - another enabler that curbed my anxiety towards fitness related confidence. Can I keep up, can I climb that, can I survive that epic? Solved the issue better than weight weenie style upgrade-itis. I no longer feel dread of lost fitness from lack of time spent on bike; I no longer dread showing-up-and-blowing-up. I don't feel a need to make a ride feel like a work-out, esp after recognizing that such leads to crashes (e.g. going hard to burn off energy in a short amount of time). Makes slogs and grinds go by quicker, and raises the minimum speed I go to offset the awful feeling of tire drag and headwind. Allowed me to choose parts for utility and reliability which add up to make the bike more of utility vehicle than a toy. Speaking of utility, it allowed me to haul a lot more stuff including hauling entire bikes to the post office for shipping drop-off, over rough and steep hilly fireroads too
Sealant for tubeless tires - must have! Keeping air in the tires has been a problem that plagued the bicycling experience, and riding on the side of roads to get to the trailhead often results in a bunch of goathead thorns in my tire
Remote dropper post - unlocking the suspension travel in my legs has opened a kind of riding that I'm thoroughly spoiled by. I feel handicapped without the ability to conveniently raise and lower the saddle on-the-fly, finding my riding to be greatly compromised and my knees potentially stressed to their limits in a shorter amount of time if I try to ride with the post partway dropped. Huge utility bonus: I can put my foot down at stops comfortably.
Improved protective gear - stuff that I can wear for an entire ride without feeling I need to take it off to vent when at a rest stop or going really slow, including vented FF helmets and soft d3o knee/shin pads. I've had concussions, sprains (inc hyper extensions), and a few big gashes, but nothing serious yet, and would like to keep it that way
All-in-all these things helped make MTB more of something I can do as a daily habit that's justified by utility, rather than some expensive hobby/exercise for thrill seeking adventurers.