I hear ya.
"Simply having a wonderful Christmas time" is, to me, a very annoying song. Just that line being sung over and over and the cheesy sounding synth with the slap back echo.
I really don't care for it.
No themes are overdone. There are only so many themes, the ones that matter to us as humans. Just about the time we get jaded, here comes another generation. It's all new to them. Long may it continue.
Writing about any other subject than Jesus and God was shunned and punishable for a millennium. I bet some people thought it was pretty played out back then!
Sometimes I read J.S. Bach's lyrics about Jesus/God and I think they are so incredibly over the top that he was actually doing it sarcastically. At the time there were still prominent leaders in the church who thought a major third would make people worship Satan and therefore they needed to stick to less dissonant intervals like octaves and perfect 4ths and 5ths. They were dicks to Bach, and probably a significant reason why he wasn't particularly popular in his day even though he was almost indisputably the greatest composer of his time.