This is now true in most companies now as Open source projects are doing the same thing. Look at Apache Spark for example which makes writing distributed programs for Machine Learning, ETL and Analytics much easier for developers.
Are there examples where doing the extra work could be better? Of course, I know that one from experience. All that time trying to integrate a CMS and a forum script and a bunch of other standalone things was a nightmare, and in that case I definitely wish I'd just rolled the whole thing myself instead.
But in many cases, it's probably better to use pre-existing solutions rather than spend all your time reinventing the wheel or falling victim to not invented here syndrome. That way, you're relying on well tested solutions with a decent amount of support available online and a guarantee it'll still work when most of your team has moved on to pastures new.
Usually theres a handful of people that tend wiggle their way into more backend, architectural things (libraries, in-house tools, etc.). If you're bored, try to be that person.
A few years ago I flipped the way I built stuff, preferring small, self-built pieces of code only I had authored, and not only was our code smaller and easier to maintain, it also significantly dropped the amount of bugs and conflicts we were having.
The problem that often happens with pre-built, well-tested solutions, is that they often only partly solve what you need to do. Edge cases might be the only cases you have, it's often better to get the one tailor made for solving your exact problem.
Also, I've found solutions custom rolled under pressure have more bugs and issues and theres never enough time to correctly debug, test, and QA before you're on to the next project.
However, CSS and HTML widgets may not lend themselves to libraries as easily as imperative programming languages.
You also, may just be solving more complex problems that require much more specialized libraries!
Just glad you found a solution that works!
Once I've solved the same problem about 4 or 5 times, I end up 'standardizing' the solution into a prototype plugin, which usually goes through 1 or 2 total rewrites, and by the time I've got the plugin resulting from that process, usually it's precisely what we need, and had all the kinks worked out.
I realize the irony here, but I release these solutions into open source and re-use them. And I know they're available for others to use and benefit from, and I fully understand why somebody like me might not actually use them directly haha. I hope people at least read my solutions in a literary sense and consider them while rolling their own solution that directly meets their own needs.