> Thinking the last part is happening or will happen anytime soon feels very naive.
"The last part" of GP is taxing the company's money when it's distributed to shareholders, and that is absolutely already happening. You might not like the current rates or loopholes (neither do I), but I think most of the somewhat-wealthy big tech engineers on this board can attest that it "is happening".
The more you concentrate taxation via capital gains, the more you incentivise the type of tax strategy where people just leave the state/country before cashing out. Countering that with exit taxes and such is hard.
Taxing company profits directly may be less efficient from an economics point of view but it's much more politically palatable.