A ranked choice type system would mean a third party wouldn't be just something that screws up elections. In fact it would probably really benefit Democrats as people who might not go to vote otherwise might go vote green as their top pick and then vote Democrat as their second pick. If the Green candidate won, that's someone they could make some compromises with to get legislation passed. If the green candidate loses, then many of their votes would go to the Dem candidate making it more likely they would win.

Twice in this century a GOP candidate has won the EC without winning the popular vote. So it's obvious why the Democrats would want to get rid of that.

But as it stands voting third party (or not voting) is just letting everyone else decide how things should be. The way it works now is you vote for the candidate most likely to care about your concerns (and who could feasibly win) and write to them and tell them what you want. Yeah it's a pain in the ass to write to a representative, but it's more likely to have an effect than anything you write on the internet. Be polite, tell them the things you want that can be reasonably be implemented. Also you're probably going to have to vote in many elections to get what you want. But if it's something you really care about you're willing to vote in as many elections and write to your rep as many times as needed to get it done.

It takes time, but it's more effective than doing nothing.