Yeah the second game wasn't a great idea, imo, but at least they did try to innovate rather than just copy their first game. Can't fault them for trying something different. Nowdays most games just stick with what sells and never try something that's radically different from what is safe. The only modern example I can think of is Fallout going from turn based overhead to semi turn based FPS. It did better than Zelda 2 at least.
The first game needed no improvement. At the time it was THE game.