About that discussion, I think I can collaborate since I've been using Renpy for a little over 1 year.
I don't follow the Summertime Saga so closely and I've never seen the game code, but I know that the developer seems to have a lot of difficulty applying certain things in the game and features that are guaranteed by default in Renpy, like support for old saves, don't work in their game.
I believe there are two possible explanations for the problems they face with the engine:
1. At the beginning of the game's production, they understood that Renpy only supports linear Visual Novels and decided that they would need to use more advanced Python functions if they wanted to create the game that they envisioned. They then created some basic functions and built the whole game on top of them.
2. they consider the limitations of Renpy for minigames as a determining factor
If Case 1 happened, then I believe that the developers were wrong when they evaluated the possibilities of the engine initially. Renpy supports a game with the same Summertime Saga features only with the basic functions of the program. This includes: open world concept, characters available in several different locations at different times, non-linear stories, repeatable events, dating sim elements, etc. I guarantee 100% that it is possible to recreate all important parts of the Summertime Saga without using a single Python line. The only difference is that the code would be less optimized and developers would probably spend more time to apply certain things in the game.
What probably happens, in my opinion, is that programmers have tried to reinvent the wheel and have made the engine less able to support a game like Summertime Saga than Renpy is originally. It is not normal for a game like Summertime Saga to have 200 bugs with each update. Even less normal is the new content breaking old content. This demonstrates that the code is a total mess and most likely harder to work than a pure Renpy code (which would be enough to recreate almost the entire game).
The second case is related to minigames. In fact, some of the minigames apparently "expand" the engine's possibilities. But then a more critical assessment is needed. Does it make sense to spend time and effort on minigames? I may be wrong, but I would say that 99.9% of players are more interested in the relationship with Roxxy or the Mom (I forgot her name) than collecting dick-shaped vegetables in the garden
.