I am building an app that is for a niche market, and I wouldn't have started without LLMs.
The hard part of this app is great design, requiring intentionally designed workflows and lots of real world testing. The code isn't the interesting part and now code isn't taking most of my time. It's great!
Once the design is nailed down and workflows tightened up, I don't expect much active development and can focus on distribution and marketing.
As a solo dev, this feels totally doable but ask me in 6 months.