I was able to do all 3, and thought it showed I was a real hard workin' go-getter to have a full time job and a full time startup I was working on. Until the startup program coordinators found out I was working a job along with my startup and almost kicked me out of the program.
It was then (actually, years later) that I realized I wasn't doing 2 jobs full time; I was doing 2 jobs part time, and that what makes the people who can run a successful startup while working on a career exceptional is just that, they're exceptional at both.
I think a lot about how much further I could have gotten with that startup if I had just quit my job and actually worked full-time on it, especially given that the program paid a stiped, instead of trying to sneak some code in whenever my boss wasn't asking for something else.
So I wouldn't say impossible, but really tough for anything big enough to be its own business.
On HN, and such, people call everything a side project due to fear of criticism. If you say "it's a side project", and people criticize it, you can say "it's just a side project".
Statements like "everything is unique" are very obfuscatory. How am I supposed to make any decisions? Yes, certain parameters might be different but a universal truth accounts for this.
Instead of posting platitudes, post a rebuttal. Post a counter-example.
1. The business world is competitive.
2. Some people are working on their ideas full-time.
Then how is it not a huge disadvantage to not be working full-time on your idea? I'm very curious how people who advocate for side projects think about this differently? With ones they hope will become successful businesses at least, other side projects, such as open source projects, make perfect sense.
I also think that this meme is alive because people are working on their startups and are hoping for them to take off. In some sense, they repeat what they hope is true.
But this setup is like crunch time in game studios which is agreed on not being very productive. Programmers make enough money that they can put some aside to have time for a startup. Unlike in other professions, there is always another job waiting if the startup was not successful. So why risk the startup by dividing one's focus?