I think all of the users here have used a site that fell into a slow or sudden decline, whether it be Reddit, Voat or something else.
In the case of Reddit, it has many problems. Money has been a big issue. The push to remove and censor certain subjects/content from the site in order to appeal to advertisers ended up alienating a lot of users who just wanted somewhere to post/look at stuff and not have it taken down. Going way way back, you could say it started with /r/jailbait, which (I think) was the first sub to be banned. It was definitely the first high profile sub to be banned. The admins were not giving mods the tools they needed, mods were taking things down even though there was nothing wrong with the posts at all and subs started being banned left right and centre. However, Reddit is still around and it seems to be doing just fine, nothing more than a blip on the radar.
Voat benefited directly from the shit happening on Reddit more than once. It started to be linked more and more as more subreddits were banned, more users were banned, Victoria was fired, the blackout happened, Ellen Pao became synonymous with Adolf Hitler etc. This had the effect of bringing everyone who was not wanted on Reddit over to Voat, making it an anti-echo chamber in relation to Reddit. Voat also has a money issue - they aren't really getting any. Another anti-attribute that can be applied to Voat is they are very very very cautious when it comes to banning things or removing things, because they know that censorship is killing Reddit. Unfortunately, this has led to shit content reaching the frontpage every day, a spam problem and the formation of protectvoat, which is basically the same as /r/ShitRedditSays but they claim to promote free speech on the site.
So what can be done here? Is it a roll of the dice to see if we end up with the same echo chamber that exists on Reddit or Voat? Which mistakes do we avoid and how can they be avoided?
I think this is something Reddit started to do on the defaults a few years ago. Stricter guidelines started being put in place to filter content and make sure it was on topic. The problem is they never stopped adding the guidelines. I can draw a crude comparison between this and what started to happen on ModernPowers. In the beginning, we had a very lenient ruleset, but it was continually abused and we had to start adding countermeasures to keep the game fair and organised. It had the adverse effect of making the game way harder for newer players, as they basically had pages and pages of rules to read through before they could start posting.
It is a Herculean task. In my opinion, we are better off with fewer rules than Reddit, but more than Voat. Voat has started to roll back on rules based on user input, which sounds like a nice thing, but it ends up harming subs because the people who are asking for rule removals are the same people who are repeatedly breaking them. They may not be popular, but they're there for a reason.
We might be better off writing a constitution for moderators, rather than users. Not to give moderators more power, but to try and set in stone what their responsibilities and powers are.