Samsung phones run on Google Android OS. They all become useless eventually as Samsung only updates the phone to adapt to the latest Android version while the phone is still being marketed. As soon as they issue enough new phones, they stop supporting the old ones.
Your mistake is thinking of the phone as something that has enduring value. It doesn’t. It is like a hotel room for a week in terms of the price. If you stay in a hotel for a week and pay 1250 dollars, you do not have the room afterwards. Same with a phone. You pay 1250 dollars for the phone, you get to use it for 5 years then toss it and get another. If you are smart you get a new phone every 4 years and trade your old one for a credit on a newer model.
I don’t like this forced obsolescence racket.