And the flaw of your argument: Even if there are other more important things for an application, let's just make anything else than the #1 feature shit.
I don't actually understand what you mean, here, but since you say it's the flaw of my argument, I'm very interested in it. Could you rephrase briefly?
I'm not saying it's not at all important that chat messages actually get sent, and if it happens every single day to a user, then they might well look for alternatives, but it's not of the same importance as losing a banking transaction. If accepting that occasional writes will be dropped on the floor allows you to get your product out in October instead of December, that could be an acceptable tradeoff. Certainly not every use case is like this, but some are.
I guess what I'm trying to say is this: You cannot ignore all the other features except the biggest one.