(@supernovae replying to myself because replying to your comment was bugged, couldn't post)...
I hear what you are saying. However, the Fediverse intentionally puts a lot of control into the hands of whoever is running the Instance. I, for one, do believe that the Beehaw Admins want Beehaw to be federated with as many Instances as possible. It’s very clear from their Rules and About posts though, that controlling and curating the atmosphere within this Instance is the #1 priority, and access to content for their own members is a high but secondary priority. They also did not want or ask to be such a huge destination for accounts in the Fediverse. One of the reasons I believe there are so many communities here is because Beehaw is an option for folks who want a safe and controlled platform with a broad range of topics, with discussion that fits a certain community culture that Beehaw espouses. Whether those communities are the largest or most active is not a motivating factor in their creation.
Beehaw admins seem to be placing the health of their own communities and members above the “greater good” of the Fediverse, which is precisely the kind of decision the Fediverse empowers them to make. They even said that, if necessary, they would move to a whitelist model for Federation. So no, the system will not “continue to be overwhelmed,” because the Admins have been very clear that they will take steps as drastic as necessary to maintain the community and culture they are attempting to build. That’s an entirely legitimate use for Fediverse Instances, even if it rubs many people (myself included) the wrong way.
For what it’s worth, I have another account on lemmy.dbzer0 and another much smaller Instance which have much more focused communities and open Federation, which embodies a more typical or expected Fediverse user experience. I plan to stick around Lemmy/KBin for the next year or so and watch all this play out. It’s still very early days and these things will work themselves out.