How hard is it to just use a damn <button> For a button on a web page? Basic HTML already works perfectly in a screen reader with no effort. It requires effort to screw it up.
The tl;dr is it's not about there being a way it could have been accessible it's that there was no out of the box answer that both did what the project needed and what was needed to have the button be accessible. If you are here to point out there is a way it could have been done well of course, so could everything else on every backlog of every open source project but things get taken off of the backlog by people planning work and putting the time in to do them not by people mentioning there are easy ways it could be done hence why this wasn't done (and also why this/any piece of software isn't perfect as everyone would like).
Sure, if an app is not fully translated and there's a lingering French string somewhere, submit a PR. But in this case, I don't see how this can be a serious suggestion.
By working to understand and solve the problem that seems easy on its surface, either:
1. It ends up harder than it seems. The original poster gains a better understanding of what is preventing the originally proposed solution from working, and is in a better place to judge what needs changing, and generally everyone wins.
2. It ends up as easy as it seems. Not much time is spent, the original poster makes a valuable suggestion in the form of a patch/PR, and generally everyone wins.
Unless we're now talking about how to implement buttons for the sake of talking about buttons instead of the accessibility of this project in which case I don't think that's what the PR comment was intended to discuss, rather a PR to fix the actual accessibility issues the project was originally called out for.
I.e. if you think the scope of the should be bigger to address accessibility that doesn't make 2) invalid it just means you think it should be a larger PR.
Sure it can: it'd have been zero extra work if it had been done while writing the code in the first place, but having to do it afterwards means you'd practically have to rewrite the entire thing.
That said, I wouldn't argue that the developer could easily have implemented it, otherwise I'm sure they'd have done so. I'm only lamenting the fact that it wasn't, and that it now can't be solved with a single small PR.
So incremental improvements like this can still be very helpful. You don't need to fix everything all at once.