Although the inconsistencies are puzzling, the one thing I would say is that we have little information on how "rare" it is. Plenty of people have posted on how bad they find it, but there won't be as many people posting about how bad they're not finding it.
Reporting bias, really.
We don't know what actual proportion of the player base is having these issues, just that they're very vocal about it.
While it's true that content people are less likely to leave feedback, and while not covering 100% of the playerbase of course, Steam is a pretty good indicator of a sizeable portion in lieu of that at least (for the record I don't own Odyssey on Steam myself but bought directly via the Frontier store), so I wouldn't say we're completely in the dark on this, both in terms of negative written feedback, and average player numbers dropping (something you wouldn't really expect so short after a brand new and meaty (relatively speaking) DLC drops after a lengthy content drought.
The negative feedback on Steam and other places on the internet (Reddit, Youtube comments etc.) seems to correlate with the feedback here in the forum (and quite frankly my very own experience with the game), and player number drops correlates on a more anecdotal level (i.e. activity, or rather lack thereof, within my own friendlist).
Edit - and just to add, the CEO of a company doesn't come out in public and make not one, but two posts in relatively short succession - just short of an apology - simply for the craic.