It’s hard to imagine why there’s been such a vehement defense of the img set markup. The picture element provides a wider number of potential use cases, has two functional polyfills today (while an efficient polyfill may not even be possible with the img set pattern), and has seen an unprecedented level of support from the developer community.
Great piece by Mat Marquis about the current state of proposed solutions for responsive images markup. On the one hand there is the img set and on the other hand the, to me and many other developers, much better picture element.
Make sure to stay up to date and read the whole piece.