The decay started earlier than Reagan it's not just the vacuousness of supply-side economics, if you asked me to pick a date, it'd be 1971.
[0]https://en.wikipedia.org/wiki/Governorship_of_Ronald_Reagan
Prices came down, even with stagflation, things got better.
In STEM we've seen huge stagnations in frontier research, breakthrough physics, and academic originality. And the arts are hardly in a healthier state.
Financially we're in a 30s-style depression but the media are being careful not to call it out as such.
Clearly this is Not Working.
An economy that privileges a few hundred billionaires at the expense of everyone else is not prosperous, stable, secure, or capable of real invention.