can threads not just kill all other instances with their huge number of posts that would come through and hide everything else?

This is my exact take as well. Defed if there is an issue, but wait and see first. I hate the kneejwrk reaction to circle the wagons here. I have been hating on Facebook for as long as anyone l, but this place badly needs content and users so I am willing to see where this goes.

Ask yourself why do they want to join the fediverse if they don't get anything out of it? Also, what would they be contributing to the fediverse besides more people. Every time I see more people, it's not great people, or thoughtful people or even shitty stars, it's just more people. Crowds help the fediverse how? It's like going to your quiet cafe and being overwhelmed by the sound of it.

You've probably seen this analogy because I've posted it way too much, but I think it really holds true:

I've used this analogy before, but threads is like a huge, 5k passenger cruise ship docking in a small town in Alaska. You don't have to know ahead of time that the 2 public bathrooms, one at the general store and the other at McDonalds, aren't going to be enough. You can also forecast the complaining about how everything isn't really tourist ready. It will suck for everyone. The small museum will be overrun and damaged, the people will be treated like dirt. It's an easy forecast.

Here's the important bit, just because they've never been in the cruise line business, doesn't mean you have to give them a chance to ruin your town.