Well, I'm gonna respectfully disagree with this statement here. The ability to harmonize a scale is the foundation of music theory and by definition that means you need to know the major scale. It's the Rosetta stone of western music. "Knowing" a scale doesn't mean running it up and down, though. You should know how to manipulate it in many various ways. Not getting into all that though.
But you are absolutely correct in saying it's a lifetime goal. Working on modes was one of the first tasks my teacher gave me, probably in the first week of lessons. That was ten years ago and I still work on modes at least a little every time I sit down to practice. Knowing that stuff makes transcribing so much easier rather than chasing seemingly random notes, especially when it comes to jazz. Then if you decide to get into learning more information and get into, say, the Melodic Minor, you will realize that the parent scale of Melodic Minor is simply a Dorian mode with a raised 7th. So you only have to change one note. Like wise, Harmonic Minor is simply the Aeolian mode, with a raised 7th. You only have to change one note. Knowing stuff makes moving into uncharted territory easier. At least, the concept will be easier. The execution is the trick...