Maybe waiting for a major version, perhaps 9.0… hopefully.
Not that I have any skin in that game anymore; I moved my stack from PHP years ago.
And yet millions of websites built on PHP happily serve unicode content to billions of users. Strange.
I have seen many cases of weird casing on web pages (not critical, but usually embarrasing), not knowing the backend tech, but i always hard bet its php.
I do think it's an issue, but a much, much smaller one than is immediately obvious. Most people aren't doing weird text processing on the fly in PHP.