Fantastic thread that has almost anything I currently find bad about the new UI explained.
There is one thing however that I see almost no one mention that annoys me to no end, and that is the weapon dioramas (both market and codex).
I absolutely despise the weapons being held by a warframe, the whole thing rotating and zooming in with no ability to control it. You can't even see the weapon half the time, and if you can it's tiny or covered by various warframe bits clipping into it. Instead what it should be is the weapon alone, on a background fitting to whatever UI style you chose, as a 3d model that you can rotate and zoom as you please.
This could be extended to warframes, maybe with a toggle from the current preset dioramas but at least for the weapons this is objectively the better solution.