Thumbnail generation is automatic in many games, going back 10+ years. With no effort on the part of the modder (and this includes complex custom assets like entire buildings or structures, like Rides in RCT, or Houses in The Sims). Thumbnail generation in this game is not even broken- custom models create a thumbnail with no effort, it just plain exists (taking a photo in the asset editor does not create a thumbnail, it is a reference photo for the editor. Not taking a photo does not mean no thumbnail). The issue is that the asset panels don't call thumbnails properly for things that aren't custom models, and something like that is a few lines of code, max.
This bug is one that should've been hotfixed the week the game came out, if not before launch. It was present in pre-launch streams. There's no way they didn't know about it, there's very little chance that it's a bug that takes notable effort to solve, and they still haven't fixed it...it is truly bizarre. Last I heard on Reddit it was said that it might not even be fixed in the new patch. It's a reproducible, basic bug with a simple UI element. The time between the streams and the game launching, the game would've already gone gold, which means they can't do much to it besides make patches and bug fixes in the interim, but this just went ignored.
I find it hard to believe that in 2 and a half months they haven't had a spare moment to look into it, and to me, it's a crowning example of awkward priorities and less-than-adequate QA, and that's very concerning for the future of this game. If this visible and reproducible of a bug can slip through and remain unsolved for months, I worry what kind of bugs will show up with the big patch and then also go unfixed.
Considering there were a large handful of streamers and tens of thousands of people watching them who did QA for things like this for free...they had to have known it was there, right? (Or wasn't there, lol)
As JimmiG and others said, it makes using custom content an absolute chore. This bug combined with the fact that hovering over blank icons requires a second before the tooltip shows up means that placing parks and intersections takes such a long time. Not a long time in the grand scheme of things, no, but it's still a noticeable waste of time every time. It's just not user friendly at all. That stacked on top of how the asset panels are left to right, one single row...it's a really big pain
. That's why it's such a big deal to me- It's almost assuredly a simple bug, it's a pain in the butt for the user, and it seems just plain sloppy, but it's still there, almost two and a half months later. Those 3 factors combined make it a good issue to get upset about, because it represents a lot of problems in one. Bugfixing priority, design issues, and an apparent lack of careful QA. This one bug brings all 3 of those to the surface for criticizing. It's concerning, is all.