Maybe using VLC Media Player from an early age has left me with too high expectations.
But if I have a program designed to view or edit a certain class of file, and it doesn't support a certain file format, I will blame that program.
GIMP and Gwenview have supported webp (the latter via platform image plugins that add support to other applications as well) since before you encountered them online. Maybe choose better tools.
Photoshop still won’t open it, MacOS preview opens it but then demands to convert it to tiff when you try to edit it