"solution for non-existent problems"
++. It replaced F-keys for people who were easily confused by F-keys (is that an actual audience?), and those of us who actually used the F-keys to their full potential were pissed off and loud about it.
Add on what everyone else had said: Little developer support plus Apple's typical profit-minded decision to use it as a differentiator for expensive laptops and never expanding it beyond that set up for guaranteed failure. There was no other possible conclusion for a feature no one asked for, few used, developers ignored, and Apple had no intelligent vision for why they introduced it in the first place. It was an unnecessary "we're special and different" bullet point when Apple had a moment of existential doubt about the appeal of their laptops.
So that would be my Apple rant: "special and different" does not make for essential, quality products. It makes for twee marketing copy with nothing to back it up.