The combination of these things you're mentioning is one of the main reasons, at least for me, that WFH is so much more productive. A lot of tech companies have evolved a culture and built offices that are in opposition to doing good work. Open plan offices have been the norm in my experience over the last 10 years (maybe more). Anytime interruption via Slack/Teams is the typical culture.

I was much more open to working in the office when I actually had my own office.

Well sure I do agree but I've never seen a tech company which isn't working in an open space. The non open-space companies feel even more rare than the remote ones.

So when you compare remote productivity, that's what you have to compare with.