No I don't think it's boring.
But if you think expansion is slow, I can see why. Civ 5 is really tailored around befriending city-states and/or getting luxuries, and if you don't have them, your happiness will tank badly, leaving you with maybe 3 good cities max...
There are times I twiddle my thumbs until Caravels technology so I can explore and trade more, so to me the game really slows down hard in the medieval era. Intentional perhaps? But to me that's not too common a feeling.