'Ebay had suggested a cheaper alternative though I knew that to be insufficient.'

It would probably have been ok to use the 'insufficient' label. This is the way Simple Delivery is supposed to work - it auto-churns out a label it 'decides' is right for your item, and it is ok to use it, even if it is underweight. Many sellers are understandably thinking 'this can't be right', and end up getting even more confused by conflicting advice from CS.

We are used to packing an item, weighing it, and buying the correct weight/size postage for that item. eBay can't expect everyone to immediately understand that it doesn't work like that now! It has been especially confusing for sellers to find their listings switched over to Simple Delivery - and maybe have items sell - before they have realised exactly what SD postage entails... 🤖

'I called Ebay and the person I spoke to basically said simple delivery doesn’t work well with CDs...'

That is very reassuring for all those trying to sell CDs... 😖