One thing that I've noticed about the Independent Sacramental Movement (ISM), as a practical matter, is how small the particular ministries — for want of a better term; the parishes, communities, missions, mass houses, monasteries and the organizing jurisdictions, and not to mention solitary clergy — often are. And how often they describe themselves as poor, in the sense of the ministry having little wealth or few material resources, and little focus on gathering more. (I suspect the members come from across the economic spectrum.)
Whether this is intentional, or a recognition of circumstance, can be debated though I suspect it's more of the later and having the wisdom to make the best of it. In the ISM, your priest probably has a day job, and your bishop probably does too. You might be recruited to set up the altar or move chairs because you're in rented space. There's a good bit of make-do.
I do not consider these bad, or failures — nor even exceptional. (I have a day job now and supply preach in my home church, and have moved a few folding chairs in my day.) In fact, they might be key to the ISM's long-term success, and essential for anyone who wishes to learn from them.
First, I concede that the terms small and poor are relative. I once guest-preached to two worshippers in a building so large that I could not make out their faces from the pulpit. This church had wealth and had immense capacity, but I later suspected the worshippers lived on what we genteelly call "a fixed income." (They would have been joined by a couple of dozen of their peers had it not been a holiday weekend with an unknown minister.) Was this church large or small; was it wealthy or poor?
This example is an outlier, but Protestant churches run small, and that's my background. I've often heard Protestant churches average 75 members, though it has been decades since I was in a church that large. So small, that were they Roman Catholic parishes, most would be closed by their bishops for being a poor allocation of their meager supply of priests. Protestants have a good supply of ministers, if not always in the right places! The ISM has a high proportion of its members in holy orders. So, I'll ask: what then do poor and small really mean?
The question I'd rather ask is are they (or we) sustainable? ISM churches rarely have clergy who are paid for their labor, and so far the only ISM clergy that I've heard of drawing a salary for their ministry are in chaplaincy. If they are "poor" in not having their own buildings, as is often but not universally the case, then they are rich when the termites move in. I am reminded of churches that fail under mortgages; contrary to the saying, if you build it they still might not come. I am also reminded of churches who identify ministry with having a full-time pastor. Or failing that a part-time pastor. But if the money runs out (or are unable to attract a minister; seminary debt is no small thing) then under this model, the ministry itself fails. A church that can make-do has the skills to survive.
At least, I think the ISM resets usual church expectations, by addressing sideways the perennial suspicion that all churches really care about is the members' money. Take that away and you can focus on the people and the church's mission.
They are like the small mammal that will crawl out of the ashes when we mainline dinosaurs get vaporized by the meteor. Not that it's easy, but there are worse things than being small or poor.