MAGA is a synonym for cult like behavior where the leader makes up absurd lie after lie and nobody questions it.
It does not have to be right wing, however as is becoming more and more obvious the Democrats are not left wingers.
Joe Biden goes on his CNN debate with Trump and says we "need abortion because illegal immigrants are raping women". It's becoming a competition which person can MAGA the hardest. Nobody can look at those debate statements without prior knowledge and conclude the Democrats are left wing.
No it's an acronym, you could alter it's meaning but simply saying blue maga doesn't make sense as the Democratic position is not and never has been that America is now or has ever been less than great. Ie. We have fallen and the only way to get back up is the r ticket.
It's always been America had it's problems but we can and are always making changes and working towards a better future together. Ie. Not perfect, bit actively trying for perfection and the only way to get there is together.