I think opinions were all over the place when it came out
Do we know this? We all admittedly don't have much to go on besides our memories and what remains of the press of the day, but I've seen little to suggest that there was much of anything other than a widespread consensus of the game's excellence. I remember Zelda II being the talk of the schoolyard, the headlines it made for selling out everywhere, the accolades it received in magazines (including some "Game of the Year" awards), and the immediate and obvious influence it had on subsequent NES games like Teenage Mutant Ninja Turtles, Castlevania II, Blaster Master, and Battle of Olympus.
The first time I ran into truly negative Zelda II opinion wasn't until 1998 during a conversation in the run-up to Ocarina of Time's release. The exact quote was something like, "Zelda II... wasn't that the one that sucked?" And even that carried the connotation of being a second-hand or revised opinion. I think what happened was a lot of folks had a blast with the game when it came out, then eight or nine years later when they were in a different place in life thought about it like, "Zelda II, man, I remember that game was hard!" And upon revisiting it discovered, "Sweet Jesus, this game really WAS friggin' HARD! No wonder they never went back to this!"
but looking back it stands out as being different
so while saying "it deviates from the formula" doesn't make sense, as a sequel it still went in a new direction from the groundwork set by the first game
Looking back, sure, but as I said I don't think at the time Zelda II was considered a radical new direction at all. It was more of a really ambitious extension of the first game.
This sounds so silly in retrospect but I remember more than once hearing Zelda II described as "like the first Zelda... except you can JUMP!"