Seem to be 2 key concerns

1) Many of the item specifics that people are being asked to complete are N/A to the items they sell.  Like a seller of T-shirts being asked what the engine size is.  Maybe not that crazy but close to it.

2) Time needed to complete this.

For some sellers point 2 is a deal breaker, and some small and midsize sellers are leaving the platform.  Sellers with sophisticated API software have no issue.  I have over 80,000 items in my catalogue, about 10,000 listed.  All have the item specifics and mapping it all to the relevant fields in my system took a few minutes.  Any new listing I create the item specifics are generated automatically.