The stock market indices are abstractions of real world value, as in it is impossible for them to represent real world value, and they absolutely can go up to infinity. The S&P500 is printing the value 2,881 at time of writing, and it absolutely can print 1,000,000 and beyond.
When people think about stocks going up forever, they are referring to these indices. Many people are married to one or two particular stocks that they also hope to go up forever with no particular price point in mind. All of that energy is funneled into the indices, as this is what is seen as the lifeblood of economies, it is what the governments react to and the business cycle reacts to.
These are inefficiencies, as these are not the proper things to react to, but it is the best that exists.
All the major indices, for example in the United States: S&P500, Nasdaq, Dow Jones, Russell 2000, are all calculated in different ways.
The S&P500 is a weighted average of certain variables in their component companies, Nasdaq of different variables, Dow Jones of different variables.
These indices usually are attempts to solve problems of prior indices. So the Dow Jones being the most simplistic of them all, but novel at the time.
As I mentioned earlier, the indices also are not containing the same stocks as they did 10 years ago, or 20 years ago. So it does not represent the market cap growth or contraction that is actually occurring, specifically the actual money or supporting liquidity sustaining the stock prices of the individual companies that are part of the index.
Finally, currency "manipulation" is absolutely a factor. You can't "barr" it, what you described in your footnote is not the currency manipulation that happens. Inflation happens, this is continual devaluation and that is how fiat money works. There is an unlimited supply of money for a limited supply of assets.
The standard you created to support your main thesis is unfortunately divorced from the world. Market capitalization has nothing to do with real productivity. The talking points come from the critics of capitalism in general, yes, there are unhealthy incentives for appropriating the resources of the planet, pointing out that limitation does not have anything to do with what is happening in market capitalization and the role of fiat currencies. It greatly weakens your argument to try to conform things to that position.
Only thing I would add for now is that the major company components of the major indices are not producing real physical goods. Their revenues come from ephemeral intangible resources. These are tech companies using cloud platforms, where the entire platform exists in massive virtualized computational instances that are sharing resources over physical hardware, people are exchanging infinite money for an infinitely scalable resource. In this paragraph, infinite is hyperbole for an unknown maximum, where the point is that it is counterproductive to try to rationalize what the limit is in the entire supply chain of physical hardware just to say "see there is a limit".
You have to look at macroeconomics, and study it like a capitalist, and then have real applicable criticisms which people study to improve the system, compared to trying to dismantle it.