You can add Ben Melkman to list of Skeptics (good front row MSNBC video interview on Youtube
Some factors I see as different this time period
1. Central banks are “all in” ( Exponentially Expanding balance sheets and monetizing large amounts of government debt ) MMT like .
2 Governments are all in on fiscal (deficit spending) , and Fed is Telegraphing rates pinned at zero with nearly zero chance of movement in ten years has folks Minimizing their (bond allocation in 60/40 Portfolio
3. Economic growth looks weaker now and generally tepid over next 5 years compared to prospects for those prior periods You mentioned (Can help maintain FED Reserve’s political capital to keep easy money flowing to “help economy / Main Street ) for longer Till they do (too bad their tools are tailored to Wall Street and investors )
4. Also it appears to me the FAANGS are well positioned to do a lot of the heavy lifting for years to come , they are so Cash heavy , and expanding their influence into so many areas of growth that SP market capitalization has never been so condensed into a few big players. They do have some high valuations but they should be pretty stable .Also there is a sizeable shift in disruptive technology in health care , Robotics , automation, EV and more... and the market share of these areas is forecast to grow fast . These disruptive growth companies Will have more Leeway in terms of investors willing to wait for profitability and Revenue and will help support higher market valuations