ditching C doesn't solve memory leaks but it does solve use after free. A memory leak is a performance problem that isn't generally exploitable. A use after free is almost always a security vulnerability.
You can use resources after releasing them in pretty much any language. That's maybe not as dangerous as reinterpreting arbitrary memory, but then you can also use object pools for everything in C, which is what some very high performance code I used to work on did.
