That’s true in general, but Intel Atom is quite promising IIRC, and efficiency cores + improvements to their fabs should only continue to improve the situation.
I’m not saying the old logic of “ARM is efficient, x86 is fast” isn’t still true, but it’s becoming less true, and they’re kind of converging to be similar chips but with different starting points (i.e., the needs are becoming more similar, and the differences are becoming lesser).