Echo JS 0.11.0

Who told I haven't taken a closer look? I've even starred the repo *a long time ago*.
I stand by my position. I don't consider a limitation just what's implemented in the polyfill, which is actually quite good - but also the performance impact of the solution, and the outlook of the usefulness of it. Polyfilled custom properties can't be animated, for once; and generally a bit chunk of their actual convenience comes with Web Components and Shadow DOM (which can be shimmed with *severe* limitations in IE), and in the future with all the Houdini APIs.

To quote what Echo JS' mod tracker1 said 5 months ago: "Personally, I don't support any version of IE at this point.  It's EOL, replaced and a security risk.  Not to mention the shims/shivs/transforms needed for ES2017+ are massive.  It's a  target that's not worth taking for the most part."
In short: if I *have* to support IE, CSS Custom Properties are the least of my concerns. That doesn't change the fact that *any* polyfill for IE is a remarkable effort that deserves respect.

Also, my original comment *was* about the form of the post. It seems you took it quite personally and I don't know why.