I don't think growth is neccesarily the problem by itself, it's the velocity that is the problem. Reddit had a massive amount of steady growth for years and I think it mostly stayed good. Then the Obama AMA happened, and that, in my opinion is when reddit died. The number of new users outnumbered the old users and the old users could not enforce the previously established cultural norms (some bad, some good, but that is what made reddit reddit), and made the ratio of users to donations crash. large corporations and political organizations realizing reddit was a powerful way to influence people didn't help, but I think if the old guard of reddit had bullied the new users into following the unwritten rules reddit would not be nearly as bad a dumpster fire and the userbase would not be nearly so tolerant to admin BS.