It sounds like you're assuming it's a fair game and that everyone gets to participate. The reality is most people don't get to do the things the rich get to do
Anybody can go to ETrade or Fidelity and buy an S&P index fund. (Or individual stocks, but that usually produces worse results).
carrying forward capital losses indefinitely
That may let "the rich" pay a low effective tax rate one year, but if so it means they paid a high effective rate in previous years where they had capital losses but couldn't use it to offset ordinary income. Getting rid of that offset would put an end to virtually all investing: investors would suffer 100% of their losses but keep only 85% or less of their gains, and that's not even accounting for inflation.
Anybody can go to ETrade or Fidelity and buy an S&P index fund. (Or individual stocks, but that usually produces worse results).
carrying forward capital losses indefinitely
That may let "the rich" pay a low effective tax rate one year, but if so it means they paid a high effective rate in previous years where they had capital losses but couldn't use it to offset ordinary income. Getting rid of that offset would put an end to virtually all investing: investors would suffer 100% of their losses but keep only 85% or less of their gains, and that's not even accounting for inflation.