When we look at the norms of Christian worship, there is a standard of time, however frequently it's broken. (Non-Christian Unitarian Universalists note this, too, considering where we get our worship habits.)
To put it so briefly as to risk being misleading, daily prayer should go up morning and night each day, and we should attend to the Table each Sunday, and that's excluding duplicated services on Sunday morning. Two times seven is fourteen, plus one equals fifteen. So ideally a congregation should have at least fifteen worship services a week, if not more. But who does that? Some Episcopal cathedrals, if you're lucky. And the occasional parish in Advent or Lent. But a leaner schedule is more customary, considering staffing costs or parishioner demand. Even a few decades ago, mainline Protestants would commonly have two services outside Sunday morning (Sunday evening and a midweek evening service, often on Wednesday) and communion once a month. This create a roughly the same ideal-weekly proportion of worship services over the course of a month. In short, a more appropriate rhythm developed, and one that seemed appropriately scaled. Some small town churches -- we certainly see this among Universalists -- take that to an even smaller scale. A service a month or so and communion once a year (if ever) based on the ability to secure a minister's services. (How many of us have preached on a circuit?) Indeed, include too-cold or too-hot weather, and I suspect you find the UUA's ten-services-a-year minimum. And now the ideal-weekly schedule gets pulled out over a year. But perhaps that's appropriate, given the size and resources of the congregation, and the size of the community. The rhythms adjust to fit the capacity of the congregation, which might have a much (or more) to do with leadership as money.
And so, if this is true of worship, it is surely also true of mission and education, to name two other key functions of a church. And sometimes, particularly in small churches, one function will exist to the practical exclusion of the others. We all know of churches that struggle to stage a Sunday service. And how some Fellowship-era congregations existed primarily at first as Sunday schools. Some can even exist only as mission, or at least at their mission arm. Here I'm thinking of little Universalist churches that closed, leaving a women's organization -- sometimes for decades -- is a group dedicated to fellowship and possibly for service not a valid expression of the church?
And so to my point. A church may not have the expected size or scope of activity and yet may be a genuine expression of church. It may start small, grow in size and complexity, and then later contract and simplify. The right goal needn't be continued and progressive development, but graceful adaptation to new conditions and the good sense to make the most of it.