Express is extremely mature as a backend, although you may not like the middleware patterns compared to Flask, for example. I've used Flask for years, and find these similar, with some differences.

Next.js + Vercel has strong adoption. This probably comes the closest to checking all of your requirements, although I wouldn't suggest using this for all use cases.

IMO the Node backend framework ecosystem is more mature than Python (no idea about .NET) since Python really is positioned better for data science/ML, etc.