I work in a shop where there was a significant effort in a cross-platform library a long time ago, but that old code has been showing cracks and emitting creaks ("Hey, folks, guess how many debugging hours it took to find out that lambdas didn't work here, either"). Use of the standard library is frowned upon except when absolutely necessary, so there's no avoiding the thing. From time to time someone will joust at it and pull a particularly screwball section forward a decade or two, but on the whole the old stuff is just never going away short of a catastrophe. It makes onboarding interesting, and it makes you reflect philosophically on expertise that is valuable absolutely no place else.

I work on other projects, or on my own stuff at home, and I can breathe again. I don't always need reverse iterators on a deque, but dammit they are there if I need them.

However, I have been in too much C runtime code to be entirely happy. I've seen too many super-complicated disasters, for instance the someone who really wanted to write the Great American OS Kernel but who wasn't allowed on the team, and so had to make their bid for greatness in stdio.h instead. You learned to tread carefully in that stuff, the only good news being that if you broke something it might have turned out to be already busted anyway and no harm done, philosophically speaking, I mean.

There are no good answers :-)