This is part of what's obvious. The whole thing, including this oooh aahh Rorschach part, is obvious. It's thoughts that we all had in high school, and it is hack.
You said, "Whether we think he's a hack", which fundamentally changes what is being discussed.
The only reason we're talking about this is because of Banksy. Not because it is a clever or "deep" piece. It's disappointingly surface level, and the fact that we're talking about that doesn't suggest otherwise.
Baloney. It's a guerilla sculpture put up in the center of London. My guess is we might be talking about it more if it were unsigned as a case of whodunnit.
But for me personally, I roll my eyes at all the ex-art students who always complain "it's a hack" for any piece of art that appeals to a wide audience and isn't some obnoxious 8-layers deep meaning. You literally see it all the time, and half the time it just strikes me as thinly-veiled jealousy, if not from the art student perspective than from the "I'm so much more sophisticated than the unwashed masses" perspective.
It happened on HN a few months ago in a post about Simon Berger, an artist who makes portraits with cracked glass. The artist has achieved relatively wide appeal, and many of the comments here were along the lines of "Meh, he's a talentless hack, he just stumbled along a 'cool' technique but the subjects are boring."
I'd have a lot more respect for folks that could just say "it's not my bag" and move on, rather than pretend they're so much more sophisticated than people who enjoy this art.
I went and looked at https://en.wikipedia.org/wiki/Theory_of_art but couldn't find it there. The "anti-essentialist" section is good, though, I think. It has Berys Gaut listing ten properties of art, all of which are nice-to-have but none of which are essential. Then if a piece ticks lots of boxes it's a shoo-in, but if it doesn't tick many of them you can argue about it.
Some of those involve eliciting some sort of response, but you could also have a decorative piece with this combo:
(i) aesthetic, (iv) complex, (v) meaningful, (vi) idiosyncratic, (vii) imaginative, (viii) skillful, (ix) art-shaped, (x) intentional
Which would be 8 out of 10, to which we could add "completely ignorable" and it could still be art. I don't see why attention-grabbing and provocation is important, and it certainly isn't sufficient on its own, plus it's irritating.
※ I admit that Xi Jinping wears a suit, but I'm still classifying that theory under "plausible deniability".
Who necessarily cares what the original design of Waterloo Place is for, it's also just a place in the center of London with lots of foot traffic, visibility and a ton of statues. Or that the place Banksy is from threw a statue into the river (that connection in particular is quite the stretch - are you saying all the things that happened in your home town are inherently reflections of you?).
The more I see people declare that their interpretation is "right" (just see the argument thread over whether right wing or left wing people are more likely to wrap themselves up in a flag), the more I think this is a pretty brilliant piece of art.