I think the "living community" thing is the answer to this. It' ecology.
I agree. A body of knowledge, mathematical knowledge being one of them, is a give-and-take between its producers and consumers; a market for ideas. It grows in that ecology of people with its pathfinders, specialists, generalists, historians, educators, etc. Committing to a body of knowledge is becoming part of its living culture.
Where I disagree: I believe some of the loss is inevitable. Keeping in mind the example of a body of knowledge above, as the scale of what's accumulated until now grows, the role each of us play in the sustenance of its culture shrink. This is a direct consequence of the modern developmental process (ie division of labour to the point where it feels like we are all modular parts of a much larger whole).
I can't say whether its better to focus on recovering what's lost, or, trust the process, as it were.