Old skool roadie here but started ATB riding in '84 or so. Early into the carbon frame scene with a Kestrel CS-X hardtail. But then someone finally came out with front air/oil forks.... oooh, lala!
I don't ride off-road as much these days but still get out on an early hardtail / rigid fork Stumpjumper BUT my 29er is actually a 700c full rigid (CF fork too) 2010 Giant Rapid 1. I swap between wheelsets - road and a trail / + decent O.R. cog's. Flat bar with index thumbies yet added 'road drop' bar ends. Climbs like crazy with a 34c width Vred's knobbies. I humbly say and often blow past young guys on FS 29'ers. Put me in a smooth single track - see ya. Though descents in the rough is a crawl . Still have my eyeballs and all teeth intact
Often get the chance to ride others and test new, and most definitely agree of incredible advancements. Sub 20 lbs. running 27.5 FS or some sort is where I might go to. Also, a fat bike when they hit sub-23 lbs. You clobber over things vs steering around. Floatation in muck and great on hardpack snow. Happy trails
edit: Many of todays FS 29er are heavy beast. They all take a different style of riding. Unless you have a lightweight wheelset, you've got to let go of the brakes on descent and have faith in the machine. You need the momentum to help up the next climb. The weight of them are a huge handicap.
This is where you want a sub 20 lbs goat for climbing. Carry water on your back.