After making those interfaces, the moment you need to do something that breaks those interfaces, you suddenly have a headache. I wrote a program in college that daemonizes by being an instance of a daemon class. Years later, people wanted the option to not daemonize. With C, this would be easy. With the way that I did things according to OOP principles in C++, I need to delete all of the code related to starting the program and write it from scratch.

You could say that I just did not do it right, but that is the problem. You need to know precisely what the future will want to do it right and that is never possible to know in advance. OOP encapsulation is heavily overrated. There are a ton of headaches in C++ that do not exist in C because C does not try to do these things. Ever hear of the diamond problem? It does not exist in C. Nonsensical types that span multiple lines when trying to figure out why there is a type error? Not an issue in C either.

C++ was advertised as reducing complexity, but in reality, it that encourages developers to drown themselves in complexity. If it were not for C never gaining a widespread STL equivalent, C++ would be far less popular. Sun Microsystems did make libuutil to provide such facilities, but sadly, it never caught on outside of Sun Microsystems technologies. The BSD sys/queue.h is the closest we have to it, but it is only for lists, and we need trees too to get a good equivalent to the C++ STL. That said, libuutil is available through ZFS, so it is not that people cannot adopt its awesome AVL tree implementation on other platforms. It is just that people do not know about it.