The title of this thread is clearly nonsense - there wasn't even any "Christmas" or "Easter" as we know them today for the early Christians.
However, I take the point that the entirety of Christ's life on earth should be considered important to Christians.
Just as many churchgoers (and their clergy) tend to dwell at length on just three occasions - his birth, his death and his resurrection - yet overlook what the Bible says about his life now as enthroned King, so too the JWs tend to not to focus on his early life, perhaps in an attempt to distance themselves from the later trappings of "the Christmas story".
The point about Jesus being "purely dependent on humans" is true up to a point in that he grew up as a "normal" boy, but God was observing his growing up and ensuring he was not killed by the Devil before his time (note John 2:4, John 7:6, John 7:30, etc, which show there was a series of events he had to fulfill first). So his childhood was not completely normal in that significant sense.
He still had that major "mission" lying ahead of him, and although he wasn't fully aware of everything, he must have known something about being "different" since his parents would no doubt have told him he was special, and the comment he made at Luke 2:49 suggests by then at least, he realised it.
We do not know if Satan attempted to kill Jesus while he was still a youth, although the fact that Herod sought to kill all the young boys to ensure his death while a toddler makes it possible that was not the only attempt that would've been made on his life when he was young, unless God specifically blocked any.
You cannot think about someone dying without celebrating where they come from and their life and birth
That may be so from our mortal human viewpoint, but that is contradicted by two things in the Bible.
Firstly, Ecclesiastes 7:1-4 which says "A good name is better than precious ointment; and the day of death than the day of one's birth". This is because at death you have done all you can, made your mark and achievements and built memories with others, whereas at birth you are a blank slate who has achieved nothing and not established what sort of person you are yet. Of course, you can't have death without birth first, but the fact is that one's achievements in life and eventually one's death overshadow their birth. If they do well and end their life in a good position (morally, not materially) then their life is seen as "good" and that reflects well on their birth looking back. But if they turn out to be someone 'evil', then that has the opposite effect and means their birth is looked back on as a 'bad' thing even if, perhaps, their birth was neutral and life could've gone either way from there.
Secondly, Jesus made no reference to commemorating his birth or even when it truly was, but his death, in contrast, is to be remembered and marked forever because of its universal significance. In part, this makes sense because Jesus 'birth', unlike that of any human, was not really the beginning of his existence. Also, though he was raised a Jew in Palestine, he did not adopt the views and attitudes of the people because ultimately, he was not of their origin and was looking to a higher calling and future, not limited to a specific nation or culture.
Your comment IS true of us ordinary humans though, because our place of birth and upbringing really is our "roots" (since we did not exist before), and it often rubs off on us, providing us with lifelong habits, memories and even accent and speech patterns. But this would not have been the same for Jesus.
TLDR: Although there is little about "the Christmas story" of these days that is necessary to understand Jesus, I do agree there is one aspect that is key: the fact that he grew up in the culture of the time with an otherwise normal family life of lowly standing helps us to understand how he - despite being the Son of God and having such an awe-inspiring 'mission' ahead of him - could also be truly 'human' in the sense of showing love, feeling and emotion for the suffering of those around him, and an understanding of the humble, ordinary "common" person.
Twice, he had observed all aspects of human behaviour and suffering: once from heaven alongside his Father, and now, "up close and personal" in the flesh alongside other human beings. No wonder he has deep love and feeling for the pain of humanity.
