When I look at Shopify (and we have a large number of skus 10K+, see common things like deleting products missing from the admin side of things as puzzling. Probably the majority of Shopify users have a handful of products but things that would be basic functionality seem to be missing and require all sorts of plugins to do things that should be in Shopify already. And from my limited testing of Shopify I dont see any changes or enhancements at least to cover basic funtions that should be supported.
I don't know if people are still looking for the solution but I found this app which executes a liquid script to delete all products. It offers 15 days free trial but I was able to delete 13K products within 30-40 mins.