yes definitely, fuzzer just helps you to find a potentially vulnerable code. It can be a coding error but not a security issue. Fuzzing is also difficult, you need to come up with good seed test cases and then you can use tools like AFL to mutate them.
Once a crash is found, you can look into it and see if it is a security issue. And then you will go into a whole different domain - exploit development.
Operating System has a lot of protection mechanism by default nowadays and it makes exploit development much harder than before.
Exploit development is turning a bug into an arbitrary code execution and allows the attacker to hijack the privilege of the running process.