I work on Batch Compress (https://batchcompress.com/en) and recently added WebP support, then made it the default soon after.
As far as I know, it was already making the smallest JPEGs out of any of the web compression tools, but WebP was coming out only ~50% of the size of the JPEGs. It was an easy decision to make WebP the default not too long after adding support for it.
Quite a lot of people use the site, so I was anticipating some complaints after making WebP the default, but it's been about a month and so far there has been only one complaint/enquiry about WebP. It seems that almost all tools & browsers now support WebP. I've only encountered one website recently where uploading a WebP image wasn't handled correctly and blocked the next step. Almost everything supports it well these days.
Whenever WebP gives you file size savings bigger than 15%-20% compared to a JPEG, the savings are coming from quality degradation, not from improved compression. If you compress and optimize JPEG well, it shouldn't be far behind WebP.
You can always reduce file size of a JPEG by making a WebP that looks almost the same, but you can also do that by recompressing a JPEG to a JPEG that looks almost the same. That's just a property of all lossy codecs, and the fact that file size grows exponentially with quality, so people are always surprised how even tiny almost invisible quality degradation can change the file sizes substantially.
Nothing technically objective, just the size that a typical photo can be reduced to without looking bad.
It really depends on what you're after, right? If preserving every detail matters to you, lossless is what you want. That's not going to create a good web experience for most users, though.
As far as I know, it was already making the smallest JPEGs out of any of the web compression tools, but WebP was coming out only ~50% of the size of the JPEGs. It was an easy decision to make WebP the default not too long after adding support for it.
Quite a lot of people use the site, so I was anticipating some complaints after making WebP the default, but it's been about a month and so far there has been only one complaint/enquiry about WebP. It seems that almost all tools & browsers now support WebP. I've only encountered one website recently where uploading a WebP image wasn't handled correctly and blocked the next step. Almost everything supports it well these days.