> people who grew up going to Mass on Sunday know that priests often recycle old homilies
That doesn't seem bad? You'd think a lot of the topics would be evergreen, and not everyone would be there for every service. So after an appropriately long time, why not recycle one that worked well?
The keyword is "often". As in, it's repeated throughout the year. The homily is supposed to be, but isn't always, an explanation of the Gospel story that was told just before it. So there really shouldn't be homily repeats within the liturgical calendar.
You are supposed to attend Mass every Sunday, so I don't think the priest is intentionally accomodating infrequent churchgoers at the expense of the regulars. And it's usually not a sermon that worked well, just a long meandering story, typically about a pilgrimage or retreat the priest went on 10 years ago, that doesn't really have a point to it.