I mean, yeah, in a general sense, I share the same opinion about DNS. But is the current system we have.

So DNS issues aside, at least the way that I see it, is even though certificate authorities are already kind of a central point of failure, having a six-day certificate increases that single point of failure risk. If Let's Encrypt has an issue on the scale of something that the Internet Archive had where they're down for days or a week, hundreds of millions of sites will lose their certificates. Having a 90 day cert, even a 30 or 60 day cert gives them some wiggle room in case something catastrophic happens.