Going on-site has certainly been made redundant in IT
The last 18 months have not only demonstrated that IT workers can do their jobs perfectly well from any Internet connection, it has also demonstrated that they're doing their jobs just as well - if not better - than before.
I do hear regrets about not having water-cooler conversations any more, and there is a wee bit of pining to see other human beings again, but I'm convinced that most IT workers will stand by a sizeable portion of working from home time during the week.
And I'm not talking about two days per month.
A large consulting company I work with has mandated one day per week at HQ - rotated by teams. Of course, it's a consulting company, so it figures that there are coordination meetings and such that justify bringing in a group of people so that they can exchange usefully, as humans beings do. Also of course, it's a consulting company, so it figures that, the rest of the week, the company wants it consultants working for their clients - remotely.