Maybe we're just very different. It would only take me minutes to whip up a few Django models, a few CRUD views and a Bootstrap frontend, but I've never needed to write a messaging system or DB storage from scratch (there are dozens of these off-the-shelf).
That having been said, most of my value is writing sane, readable, cohesive code that can easily be extended years later, with a minimum of refactoring. That's what has been most valuable to the businesses I've worked with, and employers love the fact that my team is the one with the lowest implementation times for new features.
Yup, everybody's different, nothing wrong with that! I appreciate people who do the work you do, but not every software company does websites at all. And even of those who do, plenty have grown to the point that off-the-shelf doesn't work anymore and some specialization is of greater value. (Think Uber, Slack, etc)
Yeah, exactly. You'd need to go to one of the big companies to need those skills, so you usually get companies who want some sort of API glued together with off-the-shelf components, mainly because smaller companies are much more numerous than larger companies and off-the-shelf is good enough at small scale.
This wouldn't cut it at the companies you mention, I agree. I think the main thing is that the actually valuable skills (being able to figure things out on your own, having an intuitive sense for when a solution is suboptimal even when you don't know the optimal solution, knowing design patterns, etc) are transferrable, so a good developer could work on either thing.
It probably wouldn't take two hours to become acclimated, but after a short ramp-up period, they'd be pretty good at it.
That having been said, most of my value is writing sane, readable, cohesive code that can easily be extended years later, with a minimum of refactoring. That's what has been most valuable to the businesses I've worked with, and employers love the fact that my team is the one with the lowest implementation times for new features.