The limits you are referring are not proper of C, but mostly of its standard library. Any long term C programmer has libraries, written by herself or by others, that will limit this problem a lot. An example, starting from your own example. I need a dictionary? I take my rax library, written for Redis. I need dynamic strings? I use SDS (and limit a lot the memory safety issues I could have). C is not well understood because it is seen as the language + its library. But the undefined behaviours and the terrible library are not C original sins, but the terrible work of the ANSI C committee. The Ansi C committee is responsible for a lot of bad things in software in recent years.
But the problem is that C fundamentally limits reusability! I have great respect for you and redis, but your examples are telling: they deal only with strings. With Rust or C++ you can have an extremely efficient, well tested, robust generic map structure that will accept any key or value types. C simply cannot do that, because of the language's limitations, not just its stdlib.
But C can be improved by adding features that allow this and there is a lot of CS experience accumulated around metaprogramming to design this without lots of pitfalls, and no one says that this is easy, this is really hard, but possible. Unfortunately, the committee plays with old and ugly macros system and a little bit with lambda which for sure is better than nothing, but not enough to make C better.
