It is, but it probably shouldn’t be any more. WebP has good support everywhere now and is slightly better than JPEG and PNG combined. (Better lossy compression than JPEG, plus transparency support, and better lossless compression than PNG). But even WebP is considered lame these days compared to the new crop.
E.g., JXL (JPEG XL) is much better WebP and is supported by everyone except Google (which is ironic since Google helped create it). Google seems to want AVIF to be the winner for the new image format, but not many others do.
Anyway, until the Google JXL AVIF hissy fit is dealt with, at least we’ve still got WebP. It’s not super great, but it’s at least better than JPEG and PNG. A lot of web developers are stuck in their old JPEG PNG mindset and are being slow to adapt, so JPEG is still hanging around.