Star Trek was never as good as you remember. It was never about "ideas," it was never "sci fi" in the narrow definition presented above, it was never NOT a caricature, and the reason it was never "cool" is because it was a plodding, meandering mess with shitty dialogue and poor production values.
True. False, true, true, true.
It really was about ideas, about building a better future, learning to put aside childish things, all that jazz. But you're also correct that it was never put together very well. This persisted into TNG, and didn't really change until DS9. That show had problems other than production value, though.