And there, ladies and gentlemen, is the source of the problem: People who think, Solving a general-purpose problem that has already been solved by somebody else will do more for me personally, than using somebody else's solution to solve the problems my employer actually has.

I remember doing that too, once upon a time. I invented a templating system based on Lisp for building web apps, back in the days when there were servlets, but no Java Server Pages (or Handlebars, or jsx, or anything we have today).

The templating system was wonderful, and it did improve developer productivity for our group, but there is NO WAY WHATSOEVER that it paid back the time I put into it.

The business would have been much better off if we'd simply used what was available and spent the majority of our time solving business problems, not developer productivity problems.

Furthermore, my templating system didn't wind up being that special. You know why? Because I wasn't really solving a business problem with it, so I had no constraints upon my design. Without constraints, such things meander from shiny bauble to shiny bauble according to the engineer's whims and fancies.

When you're solving an actual problem, you have constraints in time, resources, and solution. This forces you to create actual value. That makes what you build actually useful. But when you're building a thing because you want to play with the thing, you have no constraints, and rather than freeing you to create something amazing, this simply sucks you into making something that is worthless for anything except résumé-building.

"Ah, but my résumé," says the narcissist who feels no obligation to create value for their employer. I have bad news, and I am speaking from experience. If you build a bunch of things with way-cool tech that created no value, you become an ignorant person's idea of a smart developer.

Sure, you can get hired by people who don't really understand how to manage engineering, and they will throw money at you, but their ignorance combined with your self-serving ways will result in another disaster. Lather, rinse, repeat.

Good engineering cultures will ask you about your projects, and they will ferret out the fact that your projects did not add value, and did not "move the needle." I am not hypothesizing this, I have gone to interviews and had the interviewers grill me on my vanity efforts.

You cannot pull the wool over the eyes of anyone who has been through a cycle like this and is determined to never have it happen again. You can put lipstick on a pig, but there's no way to hide the fact that all projects like this wind up becoming ad-hoc, informally-specified, bug-ridden, slow implementations of half of the thing you should have used instead of building your own.

Now all is not doom and gloom. For everyone who has done this, either deliberately or by being dragged into one of these white elephant projects, there is a way to supercharge your career going forward.

Instead of boasting about your ability to write Lisp-based templating systems, or synchronization protocols based on Operational Transformations, or whatever it is you built, try confessing to it.

Point out the engineering experience, but then be up front that the project was a failure/bad idea. Sure, point out that you learned some great tech. But spend much more time talking about how much you learned about failure modes for projects. Talk about the scars.

Companied worth working for are eager to hire people who know better. Position yourself as someone who has learned these lessons the hard way.