I think there will always be "unconnectable" people, even in a small area, well covered by records - at least if you move near the edges of recorded time... where records probably don't cover the population all that well, after all.
I'm thinking of some profiles I have created, like the old man with an interesting death record in the very earliest church records for a parish, revealing too little of his background to ever find him where he came from as a soldier, many years ago, and to little about his last (and only known) wife to make her family identifiable. Just her very common given name and no patronymic.
I am also thinking of some other people I have created profiles for when exploring all the births in a parish a given year, a little later but still before the records are very informative about where people came from, and where they went. Those who stayed in one place are easy to identify and connect to other families - within a few generations most of the staying families intermarried. But an itinerant farmworker couple having two children in one place and then moving on, that's next to impossible... at least before all the records all the way back have been completely and reliably indexed. But there will probably still be gaps for them to fall into, even then.
