I agree with your point in general, but I think it is vastly exaggerated to call GC 'ridiculously inefficient' or 'unnecessary in general'. For many common problems, GCs add at best constant overhead. And, almost all highly performance critical programs have some kind of (admittedly specialized) GC mechanisms in place, because often releasing objects as they go out of scope is not efficient enough.

Even more, the performance limitations of most GC languages have more to do with the lack of good ways of writing code which simply doesn't allocate, rather then the problem of collection. GCs are often faster than malloc/free, but not as fast as simply not allocating/freeing anything.

Finally, it's important to remember that there are algorithms that are significantly more difficult to implement without a GC tahn with a GC. Even simple compare-and-swap atomic sets can require many times more code and care to implement if you have to handle cleanup of temporaries as well.