I have several 3x bikes in my family (I also have several 2x bikes - gravel and road). Where the triple excels is in road touring/bikepacking. Extra low gearing with small to modest jumps is needed for long, loaded rides, with wind and hills. 26/36/48 in the front and 11-36 in the back gives me 18.7 gear inches on the low end and 113 GI on the high side - all with very manageable jumps between gears to keep a good cadence and energy conserving power requirements. I generally stay in the middle for most road conditions and can find a comfortable gear for my cadence. Drop the chain on the 26 ring up front for long steep uphill grades to find 3 unique, energy conserving gears below those possible on the 36 middle chainring. Same sort of thing on the high side for couple of unique gears for the 48 big ring for downhill stretches or with a nice tailwind. With my road cadence between 75 and 85 rpms and 10 cogs on the back it effectively turns into a range of 15 unique, non-overlapping gears with this 3X. I've never had any issues to speak of with 3x front derailleurs.
3x's have a place and probably aren't going anywhere as long as people get into road touring/bikepacking.