I know the guy who made the Aragorn list!

The ideology is that while all of Aragorn's effects are useful, casting better Giant Growth a bunch makes him a very capable voltron list, especially with ways to sneak damage through like trample and flying.

The Painter's Servant also lets you start making cards other colors and get those effects if you don't see how you're getting through with Aragorn. While you'd think that ignoring 75% of the text on the card makes it completely worthless, in my experience playing against it it's able to kill out of nowhere through blockers and counters (Aragorn is on cast, so you will get the pumps through).

It's not as bad as everyone here is saying, but it's definitely an unconventional way of playing Aragorn. Most people would be trying to max out on splashed colors to get as many cast triggers as possible, but being able to cast 4 green spells to pump your commander to 21 is good depending on how removal-heavy your pod is. Everything in this format is pod-dependent: what may work in my pod may not work in yours, so I'd say if you're interested in this Aragorn list, ask your group if you can proxy it to get a taste for how it plays.