There is really nothing innovative about Amazon, really nothing. It's a web hosting company, and a huge internet shop. That's all to it.
But one definition of innovation is:
> make changes in something established, especially by introducing new methods, ideas, or products.
Focussing on the eComm side:
Amazon made and continues to make changes in how people find stuff, pay for stuff, and get stuff. Even something as seemingly simple as Amazon Prime for free+fast shipping. Or keeping a credit card on file and jumping straight to "checkout complete" first, and letting the user modify shipping/billing details for a while after the order is "complete".
None of it was invented at Amazon and all of it is trivial to implement on a small or perhaps medium scale.
Amazon's innovation is implementing Amazon.
On the inevitable "day 1", Amazon will start coasting on its structural dominance and being net-extractive from consumers and platform participants. At that point they will be ripe for disruption themselves... but if their dominance has eroded previously healthy markets (for demand acquisition, warehousing, last mile logistics, etc.), they might spend longer in senescence than they did improving things. That's why I think antitrust is a good tool, that should eventually be applied to catalyze fresh growth.