Small details. Like well templates -- they were fantastically hard to track and debug at the time, and really, did they actually provide anything in the long run? Answer was... NO. they don't. Turns out it's a LOT easier to have 2 discrete functions explicitly doing the same thing than using a template. anyone will understand the scope of each if they see them; The arguments about "simplicity" doesn't exist once you get templates involved.
So yes, you can 'template' in C as well using the preprocessor, but it's still ends up being MORE READABLE than a heap of scopeless C++.
One thing I was fond of in C++ were stacked based objects; ie, use the constructor to save some state, and use the destructor to restore it. I think it is a lovely concept, and I still miss it -- hover it's a concept 'new hires' had problems with very often -- it was not as intuitive as it felt. It turns out an explicit save/restore is better to maintain. I wish it was different, but that got THAT feature of C++ out of the window.
Anyway, long story short, I wrote zillions of lines of C++, and now I just do C. I don't have to fight with the compilers every other year for instance.
Small silly example, for a million years (it felt like it!) I could write pure virtual functions declarations as ..... int blah_blah_method(some cool parameter) = NULL; -- it actually made SENSE. Then one day, someone decided it couldn't possibly be NULL -- it had to be zero as '0' or else, no compily.
^^ that is one just a silly old single example, but theres a dozen others where your 2 years old codebase suddenly isn't compiling because someone decide to shift the language under your feet.
THAT doesn't happen with C. C just works. yes, there's lots of syntax sugar I WISH I would have been able to keep from C++, but ultimately, the possibility to write a huge pile of bloat is a lot harder in C than in C++. Some idiot 'new hire' won't make a hash objects for 5 elements.
Some idiot colleague won't decide that the string creation class constructor shouldn't take a reference, but a copy, making the app startup take 30 seconds with ONE character '&' removal.
Anyway, rant over. Regardless of what the kids says, C is nice, C is lean, C is a LOT easier to keep clean as long as the adult people using it are aware of the sharp edges :-)