Observation: Depression is a disease of the brain/mind. It skews your perceptions, befuddles your memory, saps your will, and messes with your whole experience of reality.

I have no doubt you're right - there were tons of things that used to make you (and me and us) happy. Depression is blocking our access to those memories, or mangling our memories. Even as I type this, I'm divided. Rationally I know I knew happiness. Emotionally, all the happy memories are dimmed and remote.

Treatment and/or time may restore some and maybe all that has been lost. In my own case, I'm not confident. May that not be the case with you.