not to be super deep about the 'a miku who can't sing' movie, but something I liked about it a lot is how it's centered on the need for people to create, because technology can never replace human creativity and heart in a way that allows it to truly connect with other people
miku is trying to reach a bunch of people who are so burnt out, apathetic and exhausted about trying and not making it, that they give up on what they truly want to do
but she can't reach them with her voice because she can't sing a full song about that experience or connect with them alone
so she goes and finds the project sekai kids, because they're creative, active artists who can connect with people through different forms of outputs and, ultimately, when miku can't reach people, they can
they use miku as a starting point to create different songs that apply to the creative signature and the spirit of each group, and that variation in perspective (that only human experience can provide) is what ultimately does reach people
for leo/need, it's a song that goes like 'hey, you're sad, I'm also sad sometimes, if it's too difficult not to be sad right now, let me throw you a hand and let's take step by step together'
for more more jump! it's like 'don't worry, I know things can get bad, but you can totally do it, a failure doesn't mean it's all over'
for wonderlands x showtime it's a chorus of voices showing fear and uncertainty and one relentless (emu) voice going like 'breathe with me and carry on because I believe in you and you should to'
for vivid bad squad is the direct approach of 'punch that self doubt right in the face, prove it you can do it, no matter what, you're still yourself'
for nightcord at 25:00 it's like 'I go to that place a lot myself too, the bad stuff doesn't just go away, but we can use it to create something that lets us reach those who feel the same'
so, it's the idea that technology can't by itself make something that can reach the human core of the need to be creative, but that people can use it as a tool to make something themselves
something that reflects the human experience, something which would let others know they're not alone
human creativity flowing means there will be different ways to say the same things, but that variation in perspective will be crucial in helping the message reach people who's experiences connects the most to one of those ways
it's never a waste to create from the heart
which is what people in real life have done through vocaloid all this time, starting out careers for immensely creative artists, who go on to fill the world with their own art and still go back to miku and vocaloid sometimes, like yonezu kenshi, for example
it's both the idea that technology alone can't connect to humanity without the human creative input to give the message the soul it needs, and also that no matter how many times a message is shared through art, your unique perspective of it is needed to reach someone out there who needs to hear it right now the way that you say it
and through the narrative use of a hatsune miku who can't sing