Import saidWhile I totally understand where you're coming from.
It seems a bit nit-picky because being that it is a holiday that also marks the unofficial start of the summer season--- many people are out and about at the beach, pool, bbq-ing, gathering with friends and family, etc....which are generally happy things.
We understand it's to honor the dead.... most average Americans see it as a day off from work--- an opportunity to enjoy the warming weather, and a good time to host family and friends for a BBQ and whatnot.... So Happy Memorial Day to all......and let's not forget it's meaning to reflect upon those who have died serving.
And I get your point as to the evolution of a holiday though I'm not certain my comment on a Happy Memorial is nitpicky as it seems kinda in yer face, especially, I would think, it must sound even insulting to a parent who lost a kid to war.
Mostly it points to the lack of expression in English which is odd because, as you know, we have at least 57 words for all the subtle differences of snow, but do we have a word for greeting a solemn occasion? How about a solemn occasion with picnic at beach? Snow38?
Yiddish might have something close, gut yontif
or good holiday which can but doesn't necessarily convey a sense of festivity.
What do you say to someone marking the anniversary of a loved one's death. Happy Anniversary?