We (coders.fail) have some Shopify apps. If you stay on it, have a good USP and marketing, it can definitively work. I know some people who did it and are happy. We didn't focus enough on it and are currently working on something else.
I'm always of the opinion to not put your eggs all in one basket, at least when you have some eggs. Starting out and working on some apps that give you some income, seems like a good approach.
If you have some questions, let me know.