Here are my wishlist. I'm focused on what improvements / features I would like, sorry if they appear negative
Change to xenForo
the BEV of forum software, whereas vBulletin is the dinosaur fossil equivalent of ICE. Having to click a non-obvious little icon to get to "first new post in thread" an the main link takes you to first-post. Stuff like that which was the norm 5 years ago until xenForo took a fresh approach and tidied up all that stuff.
All that QUOTE / MULTIQUOTE stuff is dire. xenForo allows you to just highlight a snippet of text and then get a popup offering to quote that. Fiddling around removing the bulk of text to just to quote a sentence, or wanting to quote multiple points from within a post ... I doubt people, in this day any age, understand all the [tag] stuff, or want to. I can't even press Control-B to boldface a word, and no WYSIWYG mode in the editor.
Get over "some people may not want to" and require Location. Its a free text field and people will put in stupid things like "on the internet", so don't have to give anything away if they are shy. For a topic like this there are huge differences between e.g. USA and UK posters.
Make the sidebar optional
edit: I just voted on the thread. That produced a popup notification which i had to dismiss, instead of just providing a visual clue that I had done that. All that sort of stuff is what I was alluding to - archaic - and vBulletin haven't grasped that, sadly.