"Is it realistic to believe we can save the planet with regulations?" ... is a horribly naive question.
We can burn all the fossil fuels we can find, dump all the waste we want into waterways, and pollute everything in every way imaginable... and the planet will still be here, we will not.
Same story, we can deploy every nuke on the planet and kill off every living thing in a haze of stupidity and lunacy... and the planet will still be here, we will not.
Truth be told, and dispensing with the traditional religious dogma, Earth has started over several times already after just about all "life" on it was taken for some reason, event, or otherwise.
Why do we regulate at all? And it is because of public interest, despite the best argument from what is left of rugged individualism and libertarianism we all share this planet. We know we impact it thus we impact one another. The condition of the planet for us to continue to live on is one of many reasons we deploy regulation. Never was an end all be all for all problems, in this case it is a method to address what we do to our planet thus do to our ability to live on it.
Not for the sake of the planet, it will carry on, it is for our sake.
The implication of the question means changing the OP's idiocy to "Should we continue to regulate so we can exist on this planet?" The answer is clearly yes. Even if it does not solve every problem we have from climate change, to population levels, to nations and ideologies that cannot get along, to dealing with famine or disease, the list goes on and on.
The real question, the ultimate question, is are we going to continue to evolve and grow up or, die off one way or another because we were too stupid to realize what we've done?