To say it’s a “modern” format implies some sort of improvement, which it is marginally, but not really. The people who made Jpeg said “here’s a lossy format, we could make it smaller and lossier, but this is probably too lossy as is anyways”. So they stopped. Webp is basically what happens when you keep going for a lossier format, and as a result is smaller. You shouldn’t use it for the same reason you shouldn’t use jpegs, lossy formats suck. You should be excited about lossless formats like pngs and svgs.
Also, there was a major vulnerability in webp that allowed people to embed arbitrary code in it like 6 months ago. How the hell is that even possible?!? It’s a static image!