Paginate the inbox (and all folders)
The new visual design is neither great nor horrible, but the implementation of "infinite scroll" for messages is the dumbest idea ever. I used to be able to page through emails, but now I have to keep scrolling and scrolling and scrolling and eventually it gets slower and slower and slower. Infinite scroll is a known performance killer, and makes it take longer to get to older emails. With AI coding assistance, it should be very easy to allow users to have a toggle switch in their settings to either have a horrible infinite scroll experience or to use a paginated UI - that way your horrible Product Manager can say they have made a change to the UI and thus they deserve a paycheck, but users also get to have a good experience.