re: There are some major issues lurking in the US financial markets

Not necessarily. You can call it whatever term you like, but the degrees of overvaluation previously observed only in 1929 have now occurred for the 2nd time in the past two decades (with a housing crisis between the two). I'm simply taking the best long-term valuation indicators out there, and seeing a likely 1/2 to 2/3 fall from the peak at around 2,940.91, based on what happens with similar deviations from the norm.

I know that the past two times the S&P 500 only dropped about 50-58% from the peak, but a lot of that is attributable to the tactics the Fed had at its disposal to postpone the full effects of the ongoing corrections. The Fed will be unable to soften the blow the same way this time around (although it will still be able to soften the blow).

There is also a solid macroeconomic narrative that supports an intuitive business reason to back up the statistics. There is too much low-quality corporate debt relative to the size of the economy, and with interest rates so low for so long, there's no good way to come back up without destabilizing the whole system. Plus you have falling unemployment and temporary stimulus that's been driving recent macroeconomic growth that can't keep going, and demographic headwinds in terms of the size of the overall labor force. On the corporate earnings side of the story, you have not enough gross domestic investment, Wall Street pumping unrealistic revenue growth projections, an over-reliance on passive investing strategies as hedge funds lose popularity, and a reversion to the mean that's occurring in the balance between corporate profit margins and wages. Against all this, you have global equities entering into bear markets around the world, FAANG and cryptocurrencies falling out of favor, and a U.S. housing sector that is starting to seriously slump (based in part on falling foreign demand from China and elsewhere) bringing an end to the wealth effect from home and stock prices. So a reasonable mechanism for the drop exists to back up the statistical argument.

This doesn't necessarily imply an economic collapse. The Fed will likely turn more dovish and revert to near-ZIRP again. More QE will go into effect. Life will go on. But first, asset prices must drop.