But realistically that only solves a tiny fraction of the problem, since realistically new greenfield projects started today will likely take 10+ years to become widely used, if they do at all.
WebP was written at a time when C/C++ was still the only viable language in which to write an image compression library. Saying "things like this should be written in Rust!" just doesn't actually do anything to make software like WebP secure. Improving fuzzers and sandboxing might.