It's the same situation with VP9. It's supposed to be a competitor to HEVC, but in reality lack of serious psychovisual optimizations in any of the publicly available encoders make it at best on par with x264 compression-wise, while being significantly more computationally expensive.
Its only appeal is that it's royalty-free, but since all devices that support VP9 decoding also support h.264, is it really worth it?
The quality of encoders have a much bigger effect on whether or not a codec is 'good' or not. LAME, mozjpeg, and x264 are great examples.
MP3 is competitive with AAC and far more compatible, if you use LAME. Same with JPEG and WebP, or x264 and VP9. All 3 of those encoders deliver higher quality AND better encoding speed than their competitors.
You are comparing an encoder (x264) with a format (VP9). While there is a reference encoder for VP9 (libvpx). x264 has been one of the most heavily optimized encoders whose development was sponsored by many different organizations, whereas libvpx did not see the same kind of love and most of the work came from Google's employees (with some from outside, I'm sure).
There exist other VP9 encoders, but all for specialized purposes.
> x264 has been one of the most heavily optimized encoders whose development was sponsored by many different organizations
No, it did not.
> whereas libvpx did not see the same kind of love and most of the work came from Google's employees.
You're getting your facts wrong: x264 was developed by a very small open source community, with at most 5 developers on it, on their free time, while libvpx got quite a few people from Chrome Media Team paid to work for years on it.
Its only appeal is that it's royalty-free, but since all devices that support VP9 decoding also support h.264, is it really worth it?