There are upsides and downsides to working in a office, something I'll readily admit as a WFH proponent. For me the upsides of being in a office are outweighed (greatly) by the upsides of WFH such that I can work around the few downsides of WFH and still be a "net positive". This calculus is different for every individual person but businesses want to paint with a broad brush, ignore that, and just have 1 policy for everyone. As other have mentioned I've sure there is plenty of middle-managers that are particularly interested in getting back to the office as some of their jobs have probably been (rightfully) called into question.
There are a TON of companies hiring remote/WFH so at this point it's almost completely up to your preference what you choose to pursue. For myself I only intend on taking WFH jobs going forward, I've seen the light and have interest in going back.
> Or is there indeed legitimate net benefit to working in offices?
Yes there absolutely are benefits to working in an office, there are also benefits to WFH. In-person meetings are the best medium we have available to us but video calls are good enough for me (and the team I work on) and the technology is only going to continue to improve as more people WFH. On the flip side nothing can beat the comfort of my house. I have my office furniture, my monitor setup, my kitchen for meals/snacks, my bed/couch for breaks, and my dog. Not to mention how easy it is to throw in a load of laundry, take the dog on a walk, start dinner prep, have tradespeople come do work, etc. I won't pretend there are no advantages to the office but like I said before, the WFH advantages are far greater for me.