I can see that, at least to some extent. Constantly throwing new songs at people will prevent them from singing well. But then I remember Scout camp, back in my youth when we sang a lot. We sang in the dining hall, at least one or two songs with every meal. We sang a lot of songs at campfires. And yeah, we sang the same songs over and over. But how many did we actually know? How many could we be counted to join in on, with only minimal instruction? My guess is, we knew better than twenty songs. And we sang them without books or instruments, with only a leader to give the beat and melody.
Still, we didn't sing hundreds of songs. (Well, most of us didn't, just some of us.) There is a limit to what a congregation can sing well. But what are the criteria for selection? Just what people will belt out? That's just using music as filler. What about content? What about the texts and how they match up with the Scripture and sermon and cycles of the Church year?
When Martin Luther began the revolution in hymnody during the Protestant Reformation, it was to give the congregation a chance to voice those parts and those prayers which had previously been performed by the choir. That means that hymns are not just stuck in for enjoyment, but are supposed to be chosen as part of the liturgy.
I think we need to think of the Church year as a set of six "seasons." Advent and Christmastide; Ordinary Time between Epiphany and Lent; Lent and Holy Week; Eastertide; Summer; Fall. Each of these periods has a character of its own. Some are set by the feasts and fasts of the Church, and others are set by the civil calendar and social expectations. So what we really need is a collection of missals in six volumes. Each of those missals could have a fairly restricted playlist, and there would be some overlap between them.
I keep chewing over this idea and thinking I ought to assemble all the materials and publish it.