Switching items in mid combat isn't easy but then again I don't really fault the game for that, it's unlikely that Link could open his bag (or wherever he stores those things), pull out a new item and ready it for use within a split second. For the boomerang you just have to be fast, remember you can just hold the L button, tap a place and the boomerang goes flying, you don't need to tap the item icon and draw a path. Also you can start the path wherever you like, you don't have to start drawing on Link.
As I said, I don't think the game would have been more than a rehash if they had stayed with button controls, there have been 6 Zelda games with that pretty much all using the same items and I doubt there's much that can still be done in terms of puzzles with the old mechanics.
I think some people are so used to the old controls that they don't like the feeling of having to learn controls. After all, if I could do everything easily with the old controls why should I spend an hour or two of the new game as a control nub? But the answer is that the new controls allow things not possible with the old ones, namely item use that's not restricted to aiming in 8 directions and hitting fire. The game is much less oriented towards the cardinal directions now, in older Zeldas you could only attack in four directions, now you have like 32 and you can move in all of these, too. You're no longer tied to moving along a grid.