There is a difference between MS, Google, eBay and the rest that you ignored. The go live was October 1, 2013. So the developers had about three years to get it right for day one. In that time frame they should have had ample time for capacity testing, QA and all the rest.
The design is also completely backwards from a normal e-tailer setup, even for something like car insurance.
Go to get a quote and they want your name, address, and some other minimal to give you a rough quote for car insurance. You don't have to create an account or give out stuff that could get your life hijacked. John McAfee on Cavuto: "Obamacare Is A Hacker's Wet Dream"
Then go to Amazon without an account and you can look at something and get the price before ever admitting you have been there before.
I'm not going into the rest of the stuff. But the three years without a capacity test? How incompetent can you be?
A little bit of this and a little byte of that can cause bloatware.