I mostly agree with you, but there are cases where the problem isn't that "thing X is too slow", but "after a long period of running the garbage collector gets

I mostly agree with you, but there are cases where the problem isn't that "thing X is too slow", but "after a long period of running the garbage collector gets bogged down with long-lived cycles and dies". So I think garbage collector improvements would be really helpful. Core interpreter improvements, not so much.