This.
Everybody following this knows the game is severely undercooked. Gog received a build, judged it broken and turn down the contract as a result. One turd less in the catalog. That's what curation is precisely supposed to be about.

Windforge, Starbound, Empire Earth, Blockhood, Bubsy: RotW, Incredipede, 1849, A.D. 2044 to name a few non-treasures that GOG has obtained.

Unless you can back up your claim with facts, that sounds like your assumption more than anything... and yah... don't get me started on curation on GOG keeping the turds out, cause there's a mountain of crap games on here, both from a review perspective and quality perspective
Exactly... every person who's saying "this game looks like crap, that's why GOG passed" doesn't fly, because there are way too many games on here that are far worse than this game is/will be... I've been playing the backer builds on Steam and even in that phase, it's a far better game overall than Hello Neighbor is even after all the patches it got... the only gripe I have is they should've went with the Unreal engine over Unity for performance reasons

GOG has NOT rejected Underworld Ascendant. They apparently already had an agreement to release game on GOG from way back when but due to change in rules and curation on GOG over the years, they have to renegotiate the deal.

The new negotiations are still ongoing. The problem is, it doesn't seem the negotiations can be concluded and game listed on GOG before launch date (and there IS always the change of no deal being reached). OtherSide Entertainment is legally obligated to provide DRM-free copy for backers at launch so they're scrambling to find a way to fulfill these obligations. GOG keys for backers are still possible, devs simply can not guarantee them until the negotiations are concluded. Other options are also being looked into.

https://www.othersideentertainment.com/forum/index.php?topic=6437.msg35305#msg35305

You want to look at games like Bard's Tale IV and say that Unreal has any inherent performance advantage? Or hey, you just mentioned Hello Neighbor, another badly-running Unreal game. The most important factor is if the devs are any good at optimizing, the engine is secondary. If anything, Unreal seems to have heavier system requirements, all other things being equal, though they rarely are, so it's hard to judge for sure. In any case there's no reason for UA not to run well, aside from dev inexperience or incompetence.

Just speaking from my own personal experience... I've had more Unity games run really bad than I have Unreal Engine games

There's a high chance you've played Unity games that ran well and you had no idea, since it's not required to put the Unity logo anywhere. (Assuming the devs weren't using the free license, and if they were, it's more likely that they're new/inexperienced, so yeah the decision to force the logo with free users was probably not very well thought out.)

I always know the engine the game I'm playing is running on... been around a long time

My guess is that Unity used to draw in less experienced developers due to their licensing model, which allowed people to use it for free up to a sales limit. ($100,000) It was only relatively recently (2015) that Unreal allowed individuals to also freely use the engine. Before, you needed a ton of cash to buy a license for Unreal. Something like $2,500 for a single computer, per year. As you can expect, the talent pool for the Unreal engine mostly consists of people who had the good fortune to afford an education.

Given more time, I expect the experience level between the two environments to even out. All of those mediocre Unity games has someone gaining practical experience, slowly learning how to be a proper craftsman.

And that is exactly why you shouldn´t take neither of the keys, and just wait a month or two - I know, for a backer, that´s a pain - to see whether they will release it here or not.

And if they do, politely ask for GOG key for free, stating, that you still haven´t redeemed any.
That´s how I would do it.

Regarding the reason for not accepting this game - WTF indeed - I am not a backer and I would jump on the occasion of being able to buy it here.

reviews at the moment are not exactly favorable...

Good point, but I trust Otherside, being veterans as they are, will fix their problems sooner or later.
So if the game will appear here later on, because GOG was waiting for them to patch it up, I would definitely buy it.

Just look at the Steam reviews, 3 days after release its at mixed (40% score)

This game is a massive flop.

The game is really good... I stand by that... there's just a ton of hate on Steam for a few legitimate reasons and some not so much... a lot of people are coming down on it because it's not a true successor to Ultima Underworld and for me having never played the originals, I have no affinity to them and don't really care if it is or not... I judge it on its own merits. Now a lot of people are also complaining about the save system, which I agree, could use a rethink, but it's not a total deal breaker even in its current form, you just have to allow yourself time to fully make it through one of the levels otherwise you have to restart it from the beginning... you CAN save anywhere, but all that does is save your items you've collected, etc. Others have complained about bugs and performance, but for me, I haven't experience any bugs yet and (for a Unity game) the game is silky smooth with maxed out settings @ 1440p on a 1080 Ti

All in all, underneath the hate train, the save issues and (for some) the bugs, there is a truly good game there... the atmosphere, level design, art, the flexibility and freedom of approaching every situation with a whole slew of options is awesome

Much like The Bard's Tale IV... there's a really good game in there, but it will need a few patches to straighten out the current issues
And much like The Bards Tale IV, a lot of that was mob mentality hate... we live in an unltra entitlement minded society nowadays where if something doesn't launch and meet their exact expectations or has some flaws... review bomb... hate train... burn them at the stakes

The Steam users dont have a clue about older Ultima titles. They reviewed the game as it is.

I would bet that even without bugs or issues the game is trash. It smells like a nostalgic cash grab.