This should hopefully get better over time as some instances stick around for longer. You’ll be able to point to instances that have stuck around for a while, which means they’ll probably stick around for some time longer. The problem right now is that the fediverse and many instances are still young, and something that started yesterday is not too likely to still exist tomorrow.
i just have such a hard time wrapling my head around why the fedi is under that level of scrutiny to begin with while everyone assumed cohost would be forever. i had an account there but stopped using it years ago because half the time i tried to log in it was down! come october there will be a plethora of mastodon instances that both predate and have outlived cohost