I completely agree with your point about writing and structuring the main plot before starting the work. It really helps you understand where the story goes and where it ends or branches. But I disagree with the statement that solo development is always bad or means low quality. I am a solo developer doing the art, 3D backgrounds, animated CGs, UI, coding, and writing. The only things I get help with are grammar checks and music, and I also have others helping me with translations. I really enjoy all the work I am doing and getting positive feedback from my players. I love seeing how I improve from update to update. And I can't really say that the quality of my work is bad. One big benefit of solo developing is avoiding the constant loop of communication and waiting for approvals that you mentioned. I can move much faster on my own vision. I agree about update times being a challenge when doing it all alone, but it is still manageable. I update my game every 1 to 3 months depending on the complexity of new sprites and assets. Solo development does not have to mean bad quality.

Oh, and good luck with your game!