This is not tricky in the slightest. All the points you make are distractions from the central concept of what people understand purchasing something to mean.

This is not tricky in the slightest. All the points you make are distractions from the central concept of what people understand purchasing something to mean. The computers these people played on with auto-updates disabled, would continue to support Flash for eternity. Your points would be valid if Zynga said "the thing you bought isn't going to run on new devices". But what they're saying is "we're breaking the thing you bought because not very many people can still give us money." Purchases without a "XX years' functionality" label should be required to be functional in perpetuity or refunded.