I mean, if the spec has been stable for two decades then maybe there just hasn't been much to fix? Especially since PNG is a relatively simple image format.

Seems that logic does not apply to jpeg though.

For modern C/C++ PNG implementations, consider lodepng (header-only), stb_image/stb_image_write (single-file), or libspng (active fork focused on performance and security) as more actively maintained alternatives to libpng.

libpng updates are either already landed or nearly landed.