Been using this side for years, joined two months after founding and I don't speak up often but this time I do.
The UI change is a pain, and I don't use this word lightly. I just wanted to add another mod and half way through, I just couldn't go on anymore because it just hurt my eyes. It was like going back in time and using some old-school monitor.
And since I am on it now, it is crystal clear that the new UI was developed with mobile devices in mind, because nowadays every side has to be optimized for phones, I get that. But when does someone use nexus? I guess when they're searching for mods... for a PC game .... on their PC. The new UI is very good at wasting space: big tiles with big pictures lots of useless information (uploader, category, date of upload, how long it has been uploaded, etc.) aka wasted space... Not something you do to improve the experience of the user, instead of seeing around 6 mods before (with the same amount of information) you'll now see 2-3. And to round things up, because we wouldn't want to bother users with important information like the mod description, you'll just add big blocky download buttons on the top of the modpage! To make it extra easy for users to ignore the description and fill the comment section with questions which were already answered in the description... So why should I waste my time writing a description of the mod anyways? Just put in a fancy picture and you are good to go, I guess?
And the new UI is something that happens when you want to be all fancy and modern but forgot about the roots and usage of your platform, it is for creators to upload their work, and for users to find and download them. Again, most likely on a PC. So it is nice that you want to add some fancy keyboard functionality to make it faster to search and find mods, doesn't help much when I have to spend double the amount of time scrolling through mods because everything has to be extra big and blocky...
Cheers. Ave.