If Joni Mitchell's Blue sounds bad there is a problem. Since newer records sound ok none would have to surmise that something happened to your older records. Played with a bad stylus, stored incorrectly, played recurrent are all possibilities. Buy a new copy of one of your favorites. If it sounds a lot better than you had your answer and you will have to consider replacing the ones you really like.
The better the system the better everything sounds including bad recordings. This excludes damaged records.
The better the system the better everything sounds including bad recordings. This excludes damaged records.