He makes indie games for 25 years. They feed him and his family. That sounds very successful to me.
He really is not. The article goes into the details of the nuance of where his games are graphically.
Not to mention he specifically addresses what you're talking about.
The next step up in art quality is to add one person to his permanent team, which roughly doubles each game's budget and roughly doubles the sales needed to support that budget. That's a big step and he's not willing to take that risk. Not sure who would be in a better position than him and his wife to assess the risk for that, so it's very hard to argue with that judgement.
That's just simply not true. He just needs to increase revenue by the additional budget to support the budget. So unless he was only break even before with revenue == budget, he doesn't need to double the revenue.
It's trying to achieve a certain level of detail/realism, but it's falling short of expectations.
This might be completely intentional, to evoke a feel for games from an era that did the same thing, but comparing to Baba is You highlights the developer doesn't understand that.
Baba is You has gone completely in the opposite direction in terms of graphical detail, come out of the Uncanny Valley, and is now sitting atop Cuteness Peak.
The dev needs to decide where he wants the game to sit and why.