Since regulated capitalism inexorably devolves into unregulated capitalism, you can just drop the adjective and say “capitalism would kill the planet”. And since we’re already in a capitalist system, and have been for a while, and we’re currently experiencing it killing the planet, you can change the tense too and say “capitalism is killing the planet”. Much clearer, and equally true.
Since regulated capitalism inexorably devolves into unregulated capitalism, you can just drop the adjective and say “capitalism would kill the planet”. And since we’re already in a capitalist system, and have been for a while, and we’re currently experiencing it killing the planet, you can change the tense too and say “capitalism is killing the planet”. Much clearer, and equally true.