The difference between the two cases you have isn't anything to do with limit pushing. Instead, it's a matter of specialization. If you develop some real depth, then that's a different matter than just being a regular programmer who's been doing slight variations on the same thing for a long time.
That's not to say that the specialists have it easy, but they do have an advantage here.
I think it does though. Or at least I intended it to.
In the first case I didn't particularly mean to specialize, but just to continuously do things you really don't even know if you can, to continually push against what you think is possible for yourself: create a js framework for instance, even a terrible one that you abandon after a year and move on to a completely different project, but that requires you to dig and research and stretch your brain. The second case was more you know it's possible and it's just following a tutorial to get up to speed on the techniques; someone else did the "hard" work, and you're not really getting anything out of it.
The first thing gives you skills that age well: you'll learn about lots of gotchas about the internals of how js and presumably other language runtimes work etc, which will help in lots of different positions; the second just gives you a line item on your resume until that fad is gone.
That's not to say that the specialists have it easy, but they do have an advantage here.