>When I was at the office for a decade, 90% of the insight and productivity came from informal conversations in the hallway, lunches and things I overheard in passing
The issue is not remote working, the very thing you wrote is the issue.
Virtually every time, remote working doesn't create new issues but reveals and - embarassingly - exposes existing ones.
You can no longer take a chance by letting things such as hallway affairs become a norm and an invisible force. You need to plan everything(and know what to plan), track everything relevant (and know what's relevant), be in control of the conditions for career and team progression (and therefore know precisely what these conditions are), you need to know your stuff. You can no longer just wait for magic to happen, put people in rooms and cross your fingers. Or send them to restaurant and expect team communication to have improved to the benefit of your KPIs.
The truth is 60-80% of today's companies are terribly run. Management of these companies is playing games without realizing it.
Remote working simply requires real management for it. Real managers quickly love it as remote working basically is : output-as-a-service : no noise, just efficiency and result. But the manager more tham ever needs to know what he is doing, because remote working accelerate the consequences of managerial weaknesses. What would have tanked a company in 5 years can tank it in 5 weeks.
But the positive is that once a remote setup has been successfully established, there is an organization insanely streamlined, efficient and competitive.