If you do not have AWS access credentials, you can still bulk-import products using the Spreadr app.
Instead of 1 credit for 1 product import, it will cost 1.2 credits for each product imported. This is because the app has to purchase Amazon data from 3rd party vendors rather than fetch it via the Amazon API.
To bulk-import products, without AWS credentils you simply have to turn ON the 'No AWS' switch before clicking the 'Start Import' button.
To bulk-import products using your AWS Access Credentials simply turn OFF the AWS switch.
Note: bulk-importing products without Amazon API will take on average 12 seconds per product.