Just about all of this is wrong.
1. The mods have always deleted posts and threads. Take that from a guy that's probably had a few hundred deleted in my time here. those rules were in place during this place's peak.
2. As for the idea that we're in a club and people stopped because of that, well, that's just reaching. That's moronic. The boards were always cliquey, even going back to 2009 when I started here. I feel like I've been one of the cliquey folks. That's not the factor.
The thing is that most people came here for hot takes, engagement, and discussions with other Ravens fans. With the ever increasing prominence of Facebook and Twitter, that function mattered less, leaving only the people who came here for discourse deeper than knee jerk reactions and hot takes. And with the growth of other forums at RSR and Reddit, the already small presence of message boarders who enjoy actual discussion was spread thin and distributed between the forums.
TL;DR? People like Facebook because they only have to read a sentence. When Facebook got even more popular, message boards, which require some level of literacyy, got less popular. We're not a society that values depth or complexity in discussion.