Oh, and you can also assume that everything seemed so high and sharp compared to your previous cartridge and turnable. And after a year and a half, that sound was already forgotten and you looked at the new system with an unbiased eye.
And two more versions. 1. You said that exactly a year and a half has passed, not a year. This means that it was a different season of the year. This means the air humidity could change greatly. Humidity affects the static on records, as well as the speed of sound waves. Many audiophiles notice a strong difference in sound depending on humidity and correct this with humidifiers, since the problem is dry air. 2. Physiological changes. Hearing can be affected by blood pressure. Your hearing can also deteriorate if, for example, you work in a noisy manufacture or listen to music loudly on headphones.
Sorry for the tirade.