The decision was not a narrow one. I don't care how Roberts is compelled to describe it. It's implications should be crystal clear, and there should be no reason to believe this issue isn't settled.
If you read the decision then it's clear that it's very narrowly defined. It fits the circumstances and the laws in place in 2012. The Colorado anti-discrimination laws were tightened up since then and the Obergfell decision forced Colorado to legalize gay marriage. If Phillips were to sue under the current conditions there is no guarantee he would win.