If you pay to own a movie then yes, you should be allowed to make copies of it and keep it forever, even if the seller goes bankrupt in future. You are paying to own the movie.

If you subscribe to Netflix you are not paying to own the content, you are paying for access to their content. Therefore you cannot legally download a movie from Netflix and keep a copy forever.

However, if Netflix don’t make it possible to buy their unique content for permanent ownership, then piracy is the inevitable result and they should address that.

But let’s be honest here, none of you are intending to buy anything.