And one of the best rougelike games ever (Unexplored) was rejected by GOG....

Look, you are comparing apples to oranges. I try to explain this the best I can.

Apples are mostly round but have a small "cavity" at each end. They are usually either red, green, yellow or something in between in color, and its flesh is quite firm. The taste is quite sweet but sometimes tart. You usually peel them sideways, making a long "string" of the peel.

Oranges, however, are either orange or red in color, and their flesh is kinda mushy. The taste is mostly sweet and somewhat acidic. Usually you peel them by making long cuts to the peel from one end to the other, and then rip the peel away with your fingers. Or if you are going to make juice out of it, you just cut it in half sideways so you can squeeze the juice out of the halves.

I hope this is clear now, and you don't mix apples with oranges anymore because then we are talking about a fruit salad.

Or about orapples. The new breakthrough in genetic engineering!

As others have pointed out, I think your perception may be off. This isn't uncommon, especially if you're not seeing games you're interested in, but it does tend to skew the reality in your mind. There have been plenty of games released that aren't 'detective/mystery/crime/horror games' or 'point-and-clicks or other low input games'. But judging by some of your other threads, your tastes are rather specific, so if you're not seeing games that cater to that specific taste, your perception is going to be that the games released are all the same.

And, as for 'looking the same', I think you should go back through the recent GOG releases and really take a good look at what's been offered. Otherwise your statement just looks like hyperbole. Further down the thread is a good explanation of why that's not feasible and actually fiscally irresponsible for GOG to do this. I'm sure it's easy to be an armchair curator but there's likely a lot more to the process than you realize.

Go figure.

The game seems to have gotten rave reviews and much publicity from gaming magazines including RPS and PC Gamer. User reviews are great as well (95th percentile). Despite that, SteamSpy shows it hasn't sold well at all. Steam owners in the lowest category (0-20000) and only 14 peak concurrent users yesterday.

GoG somehow seemed to be correct in it's "niche" appeal, but it's hard to see why. Does seem to have some serious bugs from graphics flicker to sound issues to save game corruption and possible memory leaks that still persist a year after release. Possibly these came up when GoG QA'd it leading to a rejection.

You'd think with the GOTY nominations from gaming journalism, it would have sold more, but it didn't. Seems GoG was correct about it's sales potential based on it's lack of interest on Steam.

But then there is a plethora of games here on gog where that (lack of quality all together, low sales on steam or even games that were abandoned by the developers) was no issue at all.... So it appears that GOG is very inconsistent on those criteria...

First, that is no excuse for accepting a game which does not sell.
Second, I believe you are exaggerating when you say "plethora".
Third, quality is subjective.
I wouldn't call GoG "very inconsistent" just because a game no one else is buying but you want didn't get here.

Quality is easy to measure, if you take Steam as a measuring tool (as you did for sales). I am talking about those ~30% games and the ones that did not sell on steam either. So why are those here? If enough sales and overall quality are so important? Inconsistent.

How about you back up your 30% claim or the use of the word "plethora"? You clearly do not know what you are talking about. GoG misses sometimes, but not "30% of the time". If anyone is being inconsistent, it's you, as you are complaining about GoG not picking up a year and a half old game that no one bought on Steam or anywhere else despite getting the attention of the gaming media fan club which most games do not.