Let's start with some numbers that should scare you:

Products that fail despite being technically superior:    ~70%
Startups that die from "no market need":                  42%
Startups that die from "ran out of cash":                 29%
Startups that die from "bad technical execution":          3%

Read that last line again. Three percent. Almost nobody fails because the code was bad. They fail because nobody wanted it, or they couldn't figure out how to sell it, or they burned through money before finding a customer.

You can build the most elegant, well-architected, beautifully tested software in the world. If nobody pays for it, you have a hobby.