The past decades and even now, people tend to expect programmers to do everything related to tech.
This fairytale is why so many fail.
Building something people want is marketing? Requirements gathering? Business analysis? Project management? Engineering? These are just subdivisions of marketing?
It's common place now for people to think of 'marketing' as 'advertising'. It is a much more robust subject than that. This is driven largely by the product management role being so closely integrated to the engineering flow. As I understand it, traditionally product management was a marketing department role. You can see this more with non-software companies like food or transportation.
I'd say it is more accurate to characterize your points as a "marketing feasibility analysis". But this is as much my opinion based on my understanding of marketing, as it is actual "marketing of a product" per se.
Building something is certainly easy. Building something people want and works well is pretty hard. Unless you have the latter, all the sales and marketing won't do much for you unless you have an established legacy walled garden that people are forced to use.