I don’t think it was setup wrong. It would work perfectly when tested or if you tried to show someone it going wrong. It just didn’t perform well when I’d need it to most while out on the trail.
Nobody’s saying ditch 2x or 3x if it works for you. My experience on my first MTB in 2013 was that it didn’t work very well for me and it made an otherwise enthusiastic new rider unhappy with it’s unreliability.
Saying dedicated 1×11 isn’t all it’s cracked up to be is going to attract a fair bit of flame attention.
Saying 1×10 isn’t all it’s cracked up to be would be fairer because there is a range issue with 1×10 with normal cassettes and expander cogs are a bodge.
When you add in the extra 11th bail out 42T gear above a 36/37T the 1×11 range is massively expanded and very usable. I don’t personally need the 10T SRAM has where I live.
Now I’ve tried M8000 for myself on my bike and on my steep hills I’m very happy with my setup.
I can’t see how ditching a DM oval ring, chain guide, adding a double spider, two new chain rings, a front mech, a front shifter and a new cable inner and outer is going to help me now… it’s adding more moving parts that could break and more weight making it need the extra ratios it adds.