Seems that consistency is the biggest issue, based on people being divided on having bought one with no flaws vs one that's bleh. Unless you've personally played/inspected 50 guitars in a sitting, it's harder to be objective. For my part, I've seen some howlers over the years, and others that were fine.
The 70s-early 80s are seen as a funk because of the looser tolerances, specs deviating from 50s-60s, changes in lumber quality, and just weird stuff. Still, they built some premium things, like the 25/50 LPs, E2 Explorers and so on.
I suppose part of the reason why people rag on Gibson is because they tout themselves as a premium brand (also reflected in prices) with unparalleled cultural capital, so when a pricey guitar has flaws, folk see it as hypocritical. The histrionics with the bankruptcy, Henry J., and Caterpillars crawling over Firebird Xs adds to the drama. The market has changed as well – several makers play a high level game (e.g. PRS), and guitars under 1k have become amazing in the past decade, it's stiff competition. The name has power, but only so much, and it can be a two edged thing. In any case, it puts them under extra scrutiny.
I think a lot of people nowadays simply buy over the internet without seeing/playing, then they get their knickers in a wad when it arrives less than perfect. Gotta cop a feel, or adjust expectations if buying sight-unseen.