It's rhetorical of course, it's because their users are completely blind to their pitfalls after decades of use, and it seems that generation-renewal is not a priority.
Discord servers and other contemporary solutions are much worse on the long run, but it does not matter. Software is like startups, long term is not a goal when you are not sure to survive (or in that case, being used and having contributors) next week.
I don't think I've read anything that I disagree with so strongly in a while. "Software is like startups" is about as user and contributor-hostile a concept as they come.
The long term absolutely matters and projects choosing convenience today over long-term thinking are screwing over their future. It's damn near impossible to find information about these projects outside the proprietary silos they've dug themselves into and they will regret the choice one of these days when Discord or whatever proprietary service starts tightening the screws to make money.
I'm not sure what you find hostile about their web appearance. It's a light, clean page with text that doesn't throw tons of JS at you, pop-ups, or a cookie accept/reject/ponder bullshit dialog. It could use a bit of a copy edit / redo and a screenshot (I always complain when a project doesn't have screenshots...), but I don't find it hostile in the least.
GP's point is that convenience and long-term thinking don't have to be an either-or. We should have convenient tools that don't require proprietary silos but work well on today's devices and with today's use cases.
But also, part of the problem is the use of email lists. Or rather, specifically, plain text emails, because they contain pre-wrapped lines, and users often assume monospace font. You can try to reflow, but in general it's not possible to determine whether any given line break is there because the line just needed to be wrapped, or because it's actually meaningful (for code, diagram etc).