Here is the thing: netflix and spotify are not in the "my X collection" business. They sell subscriptions to content and the apps reflect that. I am 100% in your/OPs boat but i would expect (niche and /or open source) apps to pop up that just make my collections of my content from other sources nice and the way nerds like us want. We have a right under EU data portability laws to do exactly that BUT companies break the laws to prohibit users taking control of their data. The only reason this is not changing is that we are not organised and there is no funded organisation suing the crap out of these companies until the final instance to give us our data.