I think at least in the anime, kaioken serves the exact same purpose as forms of just granting Goku a massive power boost to overcome a strong enemy and much like forms is more or less forgotten about once a newer shinier one comes around (until ssb kaioken much later on anyway)

I kind of liked Ultra-Instinct at the end of Super for this reason. It's not some transformation or unlocked racial boon. It's positioned as a genuine technique achieved by removing conscious thought from the equation and allowing each part of the trained body to react on its own. Yes, we're in the divine arc, and the gods try to position the technique as divine power, but the unique simplicity of how it functions brings us back to ground from the world of legendary transformations and cyber-biological enhancements. It fits in a martial arts anime, even if the series isn't quite that anymore.

I think the core theme of hard work doesn't just die it becomes the opposite and Goku is special. If you are anyone but Goku you are just the delaying tactic until he shows up.

Only person sorta following the old hard work theme is Tien as he seems to follow the be better than you were yesterday and don't worry about the people better than you mantra.