It took DC a quarter of 2021 only to drew backgrounds (because of the tech update) such task another artist could have done for him with ease.
Not only backgrounds but cut scenes, sex scenes, etc.
The internet is filled with artists that draw porn.
And all of them are free to apply. But you know full well that it's not as easy as you want to make it sound. Those who are really into drawing porn professionally usually want to work on their own projects and couldn't give a damn about working for somebody else for a longer time, those who only treat it as a hobby have an output that's not sufficient and most of them are just bad. In reality most games simply fail (MilftoonDrama says hello) or get very inconsistent once they've got problems with their artist.
But this has been discussed in the main topic 100 times and you can read up on it there.
It's not his goal that Summertime Saga is completed faster why should it? it's a money printing machine.
I'm sorry to say that, but that's pretty naive at best. Growth is the best way to make money and SS is almost stagnating for 2 years by now (especially compared to devs like DPC or NLT) precisely because DC is so slow. If DC would have gone big, hired more people, set up a team of artists, advertised the game more, put in on steam, etc. he'd very likely make 2 or 3 times the amount of money by now. Just look at how many people stopped giving him money because they think he's slow.
Last but not least, you really think DC would be less successful with his next game, given how "bad" the 2D NSFW game market is on average? It's a market that's pretty much empty apart from a few devs who are just as slow as him.
The art we see in each update is the same as the ones from his streams (besides the h scenes which is "spoiler" content) that takes him 2 hours, 5 days a week, max.
Now you are simply just trolling, it's stupid to even claim that. None of the sex scenes, none of the important plots twists, none of the cut scenes (apart from a few) etc. are ever shown on stream. He usually streams backgrounds, spirtes and poses - with a few exceptions here and there.
Btw some of the art he is streaming we never saw ingame, like art he had draw long time ago and its still not ingame.
That's because streaming is a part of what people pay for. They expect him to stream and they expect him to draw some lewd stuff/boobs from time to time. That's why he draws stuff that's supposed to be added later... which it then usually will (apart from some very early art that was made before the reworks started).
But again, it's not the place to talk about this here.
Edit: As a very late edit, I don't want to sound like the game is actually worth 70.000$ a months - it's not. I'm just saying that it's clearly not DC's strategy to make as much money as possible while working as little as possible. There'd be better ways to do that in his position.