When people join a community, they don't just adopt the values of the community, but they also come with pre-existing values. As a community grows, it will adapt to the people who are joining it, and this may alienate the early-adopters who joined for a different reason than the people joining during the exponential or diminishing returns phases of logistic growth. This doesn't mean the community is "ruined" but from the perspective of early adopters, they might describe it that way.
This can be seen readily in the history of Islam and Christianity. As those faith communities grew, they became very different from what their early adopters experienced, because they absorbed traditions and social structures of the people joining them.
I agree with the first paragraph but using totalitarian systems as an example is a bad choice. This is about the most extreme manifestation of communities that one can think of, most of the people did not even join voluntarily but were forced into it. Most of the change likewise happened through infighting and violent schisms. And you have to consider that there is very little to in many cases no information about what these communities were like apart from their own narration, which is guaranteed to have been rewritten to fit the dogma of the time. There are very few independent accounts, if there were they didn't survive because these groups tended to destroy everything that wasn't their own.
Keep in mind the early "faith" communities were nothing like more liberal religious groups today. In Islam radical groups are more close to the original warlord days of Muhammad. Thinks something like ISIS, that's what it was originally like.
This can be seen readily in the history of Islam and Christianity. As those faith communities grew, they became very different from what their early adopters experienced, because they absorbed traditions and social structures of the people joining them.
https://www.youtube.com/watch?v=EIpW5w_Ua20&list=PLQ7Ydow-dB...