> and nowhere else for it to go
Sure there is, it can be destroyed in asset price resets or debased in terms of purchasing power by the Fed (which is what plenty of the stock market gains since 1970 are).
You could make the same claim about Japan - an extremely wealthy nation relatively speaking, with one of the world's largest stock markets. Tokyo also has very high priced real-estate. And yet the Bank of Japan is fully capable of decimating their national wealth through Yen debasement, chopping about 1/4 to 1/3 off all their wealth in the past decade.
The Japan scenario, which the US is following, is gradually eroded growth prospects as debt consumes all capital available & necessary for investment to grow the economy. Eventually you reach a heat death, perpetual stagnation and conflict with the debt load and its interest costs; which requires constant debasement of the national currency - once you can't afford the interest costs, as the US can't any longer - until you destroy enough of the debt to climb back above water and free up capital for new investment again. That process becomes an accelerating downward spiral until you violently change something in the equation (one time massive currency adjustment, spending cuts with massive tax hikes causing a severe and prolonged recession, etc).
There is a reason gold is now normal up at $1400-$1600, instead of $300 20-25 years ago. That's all dollar destruction (also represented by the skyrocketing GDPs of most nations in USD terms from 2002-2008 as the dollar imploded and by numerous other prominent commodities such as oil).
That much destruction happened due to a comparatively modest lack of fiscal discipline during the Bush years. Just wait until you see what the present course causes. The rich will not be able to keep up, and corporate earnings sure as hell can't (they're not growing much as it is). To make matters worse, the China miracle is over, the S&P group can't lean on that any longer, there's little to no growth anywhere in the largest economic zones.
The Fed will have to get more drastic by the year with its debasement efforts (aka QE aka debt monetization). There will be a tipping point (sooner than later given the rate of debt increase) where the wealth can't outrun it via traditional assets like housing or equities. Might have ten good years left of potential asset floating, where you can semi hide from the Fed in the stock market (give or take a recession or downturn that will claim some of that potential). There is nobody to buy a trillion dollars per year of new US Government debt; and nobody that is eager for $20 trillion of new debt at 0-2% yields. So from here on out, it's a Fed debasement party; asset price increases can outrun it for a while, assisted by perma low rates. That Federal debt load will hit $40 trillion in ~11-12 years however, and the heat death will climb ever closer as GDP growth sinks toward zero Japan style.