I think the issues with concurrency are at this point greatly overblown. Is it hard? Maybe, so it are a lot of things in our field. Is it phd level? Not at all, unless you are literally breaking new ground; most problems have very well known solutions.

Mutexes are a solution to the mutual exclusion problem, no more no less. Sometimes this problem can be solved by a queue, but that opens other large cans of worms like asynchronicity.

I write more lock-less [1] code than most, but I will often fall back to a mutex as the right solution for a problem given a complexity and performance budget.

[1] by that I mean code without standard use of mutexes, not necessarily non-blocking.