I saw a shift occur in the years after btcpayserver started up, nowadays of the 10+ online merchants I that I use regularly, and accept Bitcoin, I think only 1 is limited to a bitpay option, and several have a btcpayserver interface; it used to be, pre-2017, that that list would have been dominated by them.

I certainly haven't used them since 2017 (maybe once or twice when I had really no choice, but that never happens now). They are indeed utterly appalling and it's insane to think that people are actually using that shit thinking that this is how cryptocurrency payments work ...