Perhaps another way of thinking about it is that the STS doesn’t exist to help you fly the aircraft. It exists to help the aircraft fly itself, if you let go of the control column.
That’s what stability is. It could have been achieved by other means (and it largely is, because the aircraft is naturally stable by design). The STS simply makes it slightly more stable. The more stable an aircraft is, the harder it is to change flight path or speed. That is why STS always works against you when you attempt to change speed.
Boeing could have done away with STS by making the aircraft more stable aerodynamically, and we wouldn’t be having this discussion, because it would have been completely transparent to the pilot.
I’ve been flying the thing for decades, and I’ve never heard a colleague complain about STS, nor has it ever bothered me.
But Vessbot’s explanation is really good, and provides a lot more knowledge than the manuals do.