The most cogent criticism of the original post, I think, was that he was conflating cheap art with bad art. You can (and some indies do) have very cheap lo-fi art that still looks good in context. He does not, which is fine, because it is hard.
His response to the critics was basically to double down on conflating cheap and bad. Which is a bit odd! How many times can you include a screenshot of a game with cheap, minimal (or even zero!) art that people still think looks good, and complain that people like how those games but not yours, and not realise that maybe there's something that sets them apart?
Again, it's not the quality of the art, it's the overall aesthetic, and that does not require buying more art, buying better art, or learning to do better art personally. Angband and ADOM are lovely games that do not have a pixel of art (or didn't originally, at any rate; I guess there's tilesets now or something?), and I'd a dozen times rather stare at ADOM than at one of Vogel's games.
That being said, he's still ultimately right. He is a one man shop, he has an established fan base, he's turning a profit, he's doing fine. He's quite right that hiring an artist (or maybe more relevantly, an art director) to try and fix the art problem is an unreasonable gamble. So...just stand up and own it. They're ugly games, the end. He's been very successful; he doesn't need to defend himself.
Some devs make very pretty games with terrible story and gameplay, and that's fine. They don't need to post rambling defences about how their game is really just like Dwarf Fortress if you just squint hard enough. Not every game has to be good at everything!