I believe this is something to be aware of and if this is something you don’t want use GOG instead. But in reality as long as Steam exists you will be able to download and play your games. If Steam ceases to exists then you will not be able to download them, but there will be ways to still play them, if you previously downloaded them. It is not like “owning” movies on Amazon (or just recently on the Playstation Store), where you always need to stream the movies.
I believe this is something to be aware of and if this is something you don’t want use GOG instead. But in reality as long as Steam exists you will be able to download and play your games. If Steam ceases to exists then you will not be able to download them, but there will be ways to still play them, if you previously downloaded them. It is not like “owning” movies on Amazon (or just recently on the Playstation Store), where you always need to stream the movies.