> You can buy "into a market" by investing in a ETF following the MSCI EM or SP500.

Nope. A more accurate description is saying you’re buying into a specific subset of a Market by buying shares of specific companies. Hand waving them as if they are the same thing doesn’t actually make them the same thing.

The MSCI EM, SP500, etc etc are simply a collection of public companies not the market of a given country. Which is why index funds all behave in fundamentally different ways than the actual markets we’re talking about.

Now if you do want more exposure to the upsides of a growing economy there are options, it’s just not a simple as buying an index fund.