I don't know what a .webp file is but I don't like it. They're like a filthy prank version of the image/gif you're looking for. They make you jump through all these hoops to find the original versions of the files that you can actually do anything with.
Edit: honestly I assumed it had something to do with Google protecting themselves from image piracy shit
It's still bad compared to modern lossless algorithms. PNG is very old and even though PNG encoders have evolved, it is still fundamentally a decade behind modern lossless compression algorithms.
For example: JPEG XL in lossless mode compresses at least 30% better than PNG.
Also, PNG is not actually lossless in many cases. PNG only supports RGB colorspaces. If you try to store anything that's not in an RGB colorspace (e.g. a frame of a video) in a PNG, you will lose some color information as colorspace conversion is not lossless. Example of someone running into this issue: https://stackoverflow.com/q/35399677
JPEG XL supports non-RGB colorspaces so you don't have this problem.