From my observation Wesołych Świąt (used in December to mean Happy Christmas)
NO IT DOESNT MEAN "HAPPY CHRISTMAS"!!! It means "Happy Holidays"!
You wanted to write something smart and it turned out to be completely opposite. Polish is not English. "Święta" means "holidays" not "Christmas". Christmas is Boże Narodzenie. Święto is any holiday (religious or not). It's a universal word.
As someone earlier wrote "Wesołego Alleluja" is a postcard wish. No one rather says it when seeing people. It just sounds flamboyant.
If someone has more time to wish decent wishes then say "życzę Panu/Pani radosnych i spokojnych Świąt Wielkiej Nocy."
Perhaps a glance at pre-war Polish Easter greeting cards would show whether that hypothesis is true.
That's because they ARE GREETING CARDS! Wesołego Alleluja is still a greeting card standard wish. How do you know that before war people didn't say "Happy holidays" on Easter when seeing a neighbour?
What's that? Do you know that word umarlak
is colloquial and disrespectful? Such word certainly couldn't be used as a name for All Saints. Besides that Wszystkich Świętych is not the same as Święto Zmarłych.