Far be for me to defend Simple Delivery but for me as a very long term seller who had a break when simple Delivery was first introduced

it’s working absolutely fine.

That said I know my parcel sizes and only sell items such as pre worn clothes, books and CDs plus in my favour, which makes it easy for me my local very convenient and very efficient  Post Office prints off labels for both Evri and Royal Mail. These are the only two couriers I use. 
I’ve just had 2 of  my parcels sent by Royal Mail not arrive and eBay is handling everything which as far as I’m concerned is better than me having to submit the claim.

As to Vinted, which I moved to when on my break from here, the jury is definitely out. For me it works in exactly the same way for the most part, and as of yet I’ve had nothing go missing or any requests for refunds but anyone who thinks it’s the better platform you’d do well to take a look at the face book pages which are full of complaints about customer services and the use of impost. Plus every buyer wants a knock down price and thinks nothing of making ludicrous offers  - think anything up to 60% off the asking price. Such offers can be ignored or declined but there is no way to restrict them being made. At least with eBay buy now you can choose not to receive them!

Sometimes the grass on the other side isn’t always greener