Destiny is a game that is both a product and a service at the same time. You still have access to the product you paid for - all missions, strikes, and raids. They have stopped supporting certain services for players who did not purchase TTK, them being: curated weekly activites (heroic and Nightfall strikes), Trials of Osiris, Iron Banner, leveling and vendor economy, etc. If you expected to have the vanilla disc supported forever, that's just ignorant of how a persistent world game operates.