I personally think 14 is the magic number for 1x as a truly viable 2x replacement,
Viable for what purpose? For MTB and CX it’s pretty much a done deal. For most TT/triathlon it doesn’t make much sense to have a FD except for training ride purposes. Excepting may the odd triathlon with a ton of climbing.
Road and all-terrain gravel are the only real holdouts where 2x still make sense.