To keep the main question simple: why is it so hard to reply to reviews as a developer?
You can quite easily see the reviews in the developer console, but replying to them is a straight on nightmare. You can't reply to them from the reviews section in the console. But neither can you reach the review section in the app store via there. You have to go to the app store yourself, click on the reviews before being able to reply. And the user who wrote the review can't even see if the (official) developer has replied to it. I even doubt if they get a notification.
It's quite astonishing to see that Amazon is giving so much attention and information about how to communicate with costumers, but doesn't make it easy to do so.
Besides, in order to be able to write a review for an app, you have to meet the same criteria as on any physical product, which is 50 USD! That is straight on ridiculous for people who only get apps from Amazon. They will never be able to give a fair review about the apps as reaching 50 USD in app purchases is quite rare, to say the least.