The only problem is when the market is going down, most people are losing money. Therefore, people don't have any excess funds to invest when its technically the best time to invest (when the market is going down).
Your assumption is we have infinite growth on a finite planet, which unfortunately is not the case. Eventually the party will be over, and you'll be left with the tab.
Assuming growth is linearly correlated with resources. It's not, wealth can be created though cognitive effort i.e. software engineering.
> finite planet
Assuming humans are bounded to Earth for growth.
The markets are the collective reflection of humanities productive efforts in the form of currency. Saying that growth will cease to exist in the future is the same as saying humanity will cease to be productive, a bet I am not personally willing to make.
You're arguing against an implicit faith in the civic religion of infinite growth, and the cognitive dissonance this causes.