It grounds you. It humbles you. It forces you out of the insular lives we're all leading. It gives you the ability to relate to the people who should be the focus of your politics, to actually speak their language in a way that they understand, instead of speaking in code like a political weirdo, a perishable skill.
There are studies claiming that a quantifiable drop in empathy for the poor and working class is correlated with increasing wealth. Wonder is there a similar effect correlated with increased education, even political education?
It gets you offline for a moment. It gives you some intergenerational solidarity. Some inter-class interaction. Just some fucking interpersonal community activity outside your friend group, which a lot of people have the ability to avoid currently and which was crucial to any succesful left projects in the past.
Even running errands for vulnerable people during a pandemic is something, there's probably an org doing this in your area. There are people out there that aren't totally unreachable and this is a great way to connect with them.
What you said would be true for any kind of organizing you get involved in. I thought the thrust of their argument was that there are better strategies to purse which we know do work. They point to Jane McAlevey's interview and the postal service contract campaigns. I would say though it is not clear to me how I can get involved (outside of leaving my current job and becoming a nurse or post office worker or retail store worker, etc). Actually I need to look up this postal service stuff, it wasn't clear to me if that was a national thing or restricted to Philly. If you also saw Jane's interview she stresses on the importance of strategically deciding which avenues to pursue vs not. That requires some cold blooded reading and analysis. You probably can do those things in a mutual aid group too but I imagine these groups might not be flexible enough (ironically) to centralize and pursue specific agendas.
I would agree with you that if this is the only sphere of organizing available to you have at it (for instance this is the case for where I am atm - even if I might prefer some democratic centralism :) ). If you can use the resources of your organization to later make strategic choices that would be awesome (also probably not as mutual aidy anymore :) )
Edit: Ok I looked up this postal worker stuff and this happened last september. Huh I really thought they were talking about some upcoming contract negotiation this September. https://www.apwu.org/fighting-today-better-tomorrow (if I am wrong please correct me)
Edit 2: Oh wait never mind the contract is expiring this September : https://www.jacobinmag.com/2021/01/labor-union-contracts-expiring-cba-negotiation (huh better figure out how to get involved in some of these things now)