Certainly, there are some pretty entitled people on that github issue.
But this attitude is too far the other way. Fair enough, you are under no obligation to continue providing a free service. But isn't it fair to give a bit of notice before withdrawing it? Especially after doing it so consistently for so long. Not legally required, sure, but polite.
They haven't even given notice after withdrawing it! They just waited for someone to realise and ask about it.
Bear in mind that many paid for services, on a subscription basis, technically allow the seller to change (i.e. reduce!) the service at any time. If they act in bad faith to their free tier, what should you expect about their paid tiers? You could argue you also shouldn't be using paid services that could behave that way but I think you'd struggle not to.