"Momentum; i.e. the green party's candidacy is far less realistic" says Alice. "Therefore, the democratic party deserves your green vote." I don't like winner-takes-all elections since it incentives a two-party system. But despite this current state, I'd still vote for the green candidate if I preferred it over the dem candidate. Because in the long term, it gives the dems an incentive to more closely align with the greens if they want improve their chance of success.
In this sense, the green vote wasn't a distraction, it was a message. The sentiment that incumbents feel entitled to third party votes and feel that third party votes are "wasted", I find baffling. I could argue that all votes are wasted, because nobody but me voted for the Flying Spaghetti Monster. The only interpretation under which others' votes could be said to be "a distraction" rather than "political input" is if one believed in the objective superiority of their own beliefs.
I wonder if you would change your tune if (hypothetically) UBI one day gained more momentum than Universal Health Care. But in your ideal world, this could never happen. Because all reasonable people would expend effort only into the coalition with the most momentum, which A) happens to be Universal Health Care ATM and B) will only ever be Universal Health Care in the future since the positive feedback loop never breaks.