Overall it's a clean and friendly design, and looking much more modern than the retro-nineties-aesthetic of the current site.
I've got a background in user interface and user experience (although I'm by no means an expert on that), so I'll write my impressions and reactions. My browser is Chrome 92.0.4515.159 for Windows.
In the header "We have videos of all the popular franchises: from Super Mario Bros." etc, I'd expect the franchise names and genre names to be clickable and lead me to these movies.
At top of the screen, I'm surprised that "TAS videos" stands for (T)ool (A)ssisted (G)ame movies. Wasn't it (S)uperplay?
The menu on the top of the page is too dark to easily make out, and I'm confused why the leftmost button (home) is actually a pulldown when the rest aren't.
In the box "TASVideos News", if I right-click on an article and select "open in new tab" then that doesn't work.
If I click on the bottommost news item, then the news does appear but I have to scroll down to read it; it should scroll down automatically.
Seeing the date for a news item is good; seeing the time (5:18 PM?) strikes me as overkill. Latest publications don't show time-of-day either.
In the box with the featured run, I'd expect the title ("N64 Super Mario 64 "1 key"") to be clickable and lead me to the run's info page. I'd expect clicking on the screenshot to play the movie. I'm not sure that the blue box "featured" adds anything, it looks a bit off-key.
In the box with latest publications, I'd expect the publication title ("Donkey Kong 64") to be clickable and lead me to the run's info page, which does work in the Newest Submissions box. Latest publications is also missing the branch name.
Newest Submissions should have the same column order as latest publications, so date/game/time/by instead of title (not "game"?) / branch / time / author (not "by"?) / date.
Under "Newest User Files", the "More WIPs" is a purple button, whereas in earlier sections it is simpy a text reading ("more..."). On the front page of the site, the acronym "WIP" should probably be spelled out, as it has
numerous meanings.
Movies page,
Hovering over the lightning bolt icon gives me a popup what the icon means, but hovering over the star icon does not.
I'd expect clicking on a movie's screenshot to play that movie.
There are two buttons "A/V file via bittorrent" and "A/V file via bittorrent compatibility". These are, respectively, an MKV file and an MP4 file; so clearer to label the buttons "MKV movie via bittorrent" and "MP4 movie via bittorrent". Although I understand the term "A/V file", I've not encountered if before.
On a page with a list of movies (e.g.
https://tasvideos.mistflux.net/Movies-DOS-DOOM-Stars ) clicking on any movie's "publication" button just shows you the same screen with that movie again; this button seems not useful on the list page. The list page is missing the "discuss" button.
Welp, I'll shut up for now. HTH :)