Webp is really a must for SEO… Google made it so google likes to see it. In our agency we have greatly improved our seo scores with the implementation of webp. Note that we already had implemented various formats (with picture tag) which already improved our scores but webp is a must nowadays.
But I can clearly understand that compression can take a lot of time and adding this new format could be an issue. So it should be optional (and maybe even under an advanced menu). If you don’t want it, don’t use it by default but if you want to increase your seo score, use it definitely !