Test in screen readers and see how content is being announced.
Lists have certain semantics which are very useful. Definitely good in navigation (aka nav > ul > li).
Grids are also useful BTW—we don’t have specific “grid” tags in HTML, but using ARIA attributes you can set up grids which might map onto div tags or even custom elements.
Personally, I’m much less concerned about ul/li than I am “div tag soup” which is a plague upon modern web development. Use div tags sparingly, and almost always see if you can reach for either (a) a more semantic HTML tag (e.g., key/val pairs should probably be dl/dt/dd tags, not list tags), or (b) custom elements…yes, authoring tags with one or more hyphens which are purely for developer comprehension and hanging CSS off of is perfectly fine—recommended in fact—and in some cases if you need some JS component logic as well, then boom you have web components.
My hot take is that short-term posture doesn’t matter all that much. If you have bad posture but you get up every 20 minutes and stretch/do chores/exercise for 5-10 minutes, you probably erase the original issues.
My one-two punch, if you’re looking for advice: make sure you use a chair that makes good posture easy, with your keyboard+mouse & monitor height well separated on your desk (if computing’s the main thing you’re doing as you work). And then make sure you’re getting a lot of activity throughout the day. Spans of 2, 3, 4, etc. hours just sitting at your desk will be really bad for you, no matter how good your posture is.
I guess what I’m saying is if you can either focus a lot on posture or focus a lot on physical activity routines, prioritize the latter. But both are certainly important.