It definitely still is a hardware problem today - humanoids force you to miniaturize gears, motors, and other parts (especially with the hands) which make them incredibly fragile and inaccurate. You're basically fighting against the laws of physics, so improvement on this front has been pretty slow. And tactile sensors which are key for complex manipulation tasks are still a far way to go in terms of resolution and reliability - so most robotics startups tend to rely on cameras for everything.
I think that in order to have humanoids that are actually capable of matching or exceeding the actual mechanical capability of humans, you need large advancements not just in AI but in material science as well - no machine can still match the efficiency of humans with its biological muscles, tendons, the skin / fat that surrounds them, and its vast array of sensory input.