Sometimes 'better-but-not-good-enough' is a trap. That's basically what Jeff Vogel is saying about moving up from his poor inconsistent art to slightly better art, but it's also how I feel about moving up from ascii characters to his style of "crappy" art.
AdoM is a fantastic roguelike created by Thomas Biskup, which originally had you as an '@' battling other ascii characters. Later he wanted a nicer interface and went for this kind of pixely tiles, and to be honest, I don't like it (edit: I just checked again, and the art looks far better than I remember. I still prefer the ascii version, though). If you go for bad art, just go all the way, and make it look consistent.
By the way, Baba is You, referenced at the end, is an absolutely brilliant game, and while the art looks cheap like a toddler drew it, it's all animated; they have three versions of every sprite and keep rotating them. That crappy animation arguably makes it look even cheaper, but it also brings the game more alive, and it's certainly more expensive. Most importantly, though: it's a striking and consistent look.
In the end, though: Jeff had been successfully making games he loves for 25 years. Whatever he's doing is clearly working.