I think the main thing you miss with 100% remote working is what I call "corridor creativity" [0]. As good as working from home is (or can be), I do miss the serendipity of walking past someone in a corridor, having a quick chat, drawing something on a whiteboard, and then continuing on about my day. In a fully remote world, I need to organise a meeting (over Zoom) for just about every interaction, which ends up being quite a chore and far less than serendipitous.
[0]: Corridor Creativity: https://matthewsinclair.medium.com/0124-corridor-creativity-...