I've heard this expressed several different ways, like creating your own job or learning by jumping right in, and it always completely ignores the value of professional experience.
Internships and first jobs are all about learning the realities of the work world and building up your professional network. If you're trying to build a B2B SaaS app, it really helps when you understand at least one of those "B"s instead of just guessing.
There will always be anecdotes of "I started my first business at 14 and have been my own boss ever since" but my (anecdotal) experience shows that most successful entrepreneurs are people who leverage their professional experience and network in order to get their first customers, co-founders, and so forth.
"Don't write something informative and realistic, make a call to arms!"
The whole point of an internship (or underpaid, monkey coder job) is to get your foot in the door, to get some residue on your resume, and to work with a real team trying to deliver something for other people.
You're naive if you think that you, by yourself, can imitate the processes, procedures, best practices, tools, standards, guides, and mechanisms that a large company can provide, and learn from it all to boot.
I'm all about "hoisting yourself up from your own bootstraps", but sometimes you need other people. Internships are about immersing yourself with other people, not trying to take the mantle of some superhero and thinking it's going to help you fly better.
Internships and first jobs are all about learning the realities of the work world and building up your professional network. If you're trying to build a B2B SaaS app, it really helps when you understand at least one of those "B"s instead of just guessing.
There will always be anecdotes of "I started my first business at 14 and have been my own boss ever since" but my (anecdotal) experience shows that most successful entrepreneurs are people who leverage their professional experience and network in order to get their first customers, co-founders, and so forth.