I think that's mainly because the content increased that much (better poses, quests, pregnancy, cut scenes, animations, day/evening/night versions, etc.). If the game would be as simple as it was at the start, like before ~0.14, it would probably have lead to an increase in speed. But by now there's just so much more stuff in it per update, that it's really hard to compare. Else I'd say the overall focus shifted quite a bit, back then, as we see in those Jenny pics, he basically only focussed on boobs and the belly area, while everything else was "just some lines", many early characters were way too orange and the faces were really bad at times, while now every character is actually consistantly well made - across the the whole game it's one style and one level of quality.
The rig system on the other hand was mainly for added flexibilty and for keeping android players on board. Given how popular the mobile version seems to be by now, it was certainly the right decision from a business point of view.
Both of that is probably true. I mean, back when he started he still had no kids, worked all day and did even drunk night streams. Now he's got three kids etc. (all of which are currently at home thanks to Covid) which will of course impact the time he spends working to more normal hours. I mean, it's nothing new that updates take time and it's not like he's promising fast updates. The game is free, so there's no loss by not pledging or by reducing the pledge to a lower level.
The artist stuff was discussed often and I don't think his position on that changed during these last years. People are free to apply but it has to be perfect or he won't consider it, maily because he doesn't want to spend time on instructing and correcting other people's work.
