The point is, the anecdotal evidence that you mentioned has nothing to say about other points you are making.
Just because product X runs better in a use case with software Y, does not mean product X is bad.
I do not want to come across like a ubiquity fan boy, since i only use it very targeted privately but the stuff is good, it's supported and a plug and play solution without the cloud. Exactly what fits the bill for what it's asked for here.
It is run in operation by thousands of businesses. Does it have problems, sure, like every other brand.
Have run openWRT myself on one of the latest lite APs, was good. Have not noticed a significant difference in the usage between both.
No but PoE and AP helps.