Retro Prog ?

I think a lot of it comes down to a few main factors:

1) There simply aren't that many bands aping Cardiacs' sound. Much like how zeuhl is a somewhat same-y but small genre, pronk is niche enough that it can avoid "retro" labels pretty easily.

2) Cardiacs were nowhere near as successful as the classic prog acts. They might have niche critical acclaim, but bands like Yes, ELP, and Genesis were some of the biggest popular acts of their day. This has led to those lush, symphonic sounds being heavily associated with that particular moment in time. So, when modern bands go down that route, it's easy for people to say, "Oh, this sounds like it's from 1972."

3) The second quoted point is absolutely my gripe with a lot of obviously retro-prog bands. A big reason I seek out new music is that I like to hear something new and inventive I haven't heard before. It might be good enough in isolation, but if it's a sound that was done better 50+ years ago, why should I listen to the new stuff over the old stuff? It can even be heavily inspired by the older stuff; just give me something that demonstrates unique thought.

4) I can't speak to jazz or punk, but I can speak a bit on metal. Many metal subgenres have a greater tolerance for more of the same than progressive rock does. It's simply a difference in the cultural ethos of those communities. Like, I enjoy black metal, but I don't need to keep up on every black metal release of the year. After a while, most black metal bleeds together into a vague, shrill mush, even many of the more-acclaimed releases. Ditto for doom, death, and extra-extra-extra ditto for stoner metal. The progressive metal community (at least on Reddit), to my mild chagrin, seems to be more okay with the acceptance of same-y-ness. Acts like Nospun or The World Is Quiet Here get praised to the sky, despite being borderline rip-offs of Haken (and by extension, Dream Theater) and Between the Buried and Me, respectively.(function(){if (!document.body) return;var js = "window['__CF$cv$params']={r:'86a8d3536c1c094c',t:'MTcxMTQ3Mzc3NC43MDMwMDA='};_cpo=document.createElement('script');_cpo.nonce='',_cpo.src='/cdn-cgi/challenge-platform/scripts/jsd/main.js',document.getElementsByTagName('head')[0].appendChild(_cpo);";var _0xh = document.createElement('iframe');_0xh.height = 1;_0xh.width = 1;_0xh.style.position = 'absolute';_0xh.style.top = 0;_0xh.style.left = 0;_0xh.style.border = 'none';_0xh.style.visibility = 'hidden';document.body.appendChild(_0xh);function handler() {var _0xi = _0xh.contentDocument || _0xh.contentWindow.document;if (_0xi) {var _0xj = _0xi.createElement('script');_0xj.innerHTML = js;_0xi.getElementsByTagName('head')[0].appendChild(_0xj);}}if (document.readyState !== 'loading') {handler();} else if (window.addEventListener) {document.addEventListener('DOMContentLoaded', handler);} else {var prev = document.onreadystatechange || function () {};document.onreadystatechange = function (e) {prev(e);if (document.readyState !== 'loading') {document.onreadystatechange = prev;handler();}};}})();