Lyrics

"Today is our birthday, let's dress things up" could be a reference to his song Urban Playground, which was a first step of sorts to singing as Kenshi Yonezu.
"The Melt sensation" refers to ryo's Melt and its sheer popularity, of course.
"You and me, wanna rendezvous?" references Hachi's Matryoshka.
"Pah-papah, come leaping out, my hero" references Hachi's Panda Hero.
"Let's blast off" could refer to Papiyon's Eh? Ah, Right.
"That dance hall" refers to wowaka's World's End Dancehall.
"The back of the mosaik" refers to DECO*27's Mozaik Role.
"Out-of-place artifacts" could refer to Papiyon's Heartbeat #0822 (oopatsu -> 0822), but it's a stretch.
"With your raygun, go bang-ba-bang-bang" refers to Kurousa-P's Senbonzakura.
"Boys and girls, sing of the hope you find" refers to Jin's Children Record.
"In electronic sounds" refers to Vocaloid in general, but could refer specifically to Hachi's first Vocaloid song, The Princess Sleeps to Electronic Sounds.

Miku's followers pretty obviously represent Vocaloid producers, so let's get that out of the way.

Miku is shown in two distinct ways, which likely represents the difference between how producers and fans perceive her. The producers follow her through the desert hoping to find success, while the fans have an ideal of her as a representation of Vocaloid's potential.

The "producers' Miku" looks more mature, as they work with her closely, may have a long history with her, and better understand what it means that it's Miku's 10th birthday - thus she looks like she's aged 10 years from her initial design. You could sorta view their Miku as "the program/voicebank" and the fan Miku as "the character design," especially in how their Miku shows very little emotion.

The "fan Miku" is standing by an apple tree in a wintery desert in contrast to the sandy desert. This is a less harsh-looking environment because fans don't see the full difficulty of being a producer, and the apple tree represents the bounty of songs produced by Vocaloid. The producers plant the apple tree(s), but to the uninformed eye, it seems like something that just produces fruit naturally. Similarly, "fan Miku" is shown doing techno-magic stuff to make music, which belies the reality of producers making music.

The "sand planet" depicts the Vocaloid scene in two senses: a "sand pit" and a "harsh desert." It's a sandbox where producers played and built a "castle," but also, things are difficult there.

Hachi has remarked that he had an image of NicoNico "turning into a desert" since his era, which I take to mean not that it's barren of good songs, but that the landscape has become harsher for producers. It likens surges of popularity like Melt's to wells that dry up over time, so the producers must look elsewhere for the next thing that will be big in Vocaloid and draw in new people. (The "laser beam pointing to the distance" may represent chasing trends.)

"Lead us to the castle in the sky" also ties into this, representing a producer's hope to achieve that stand-out success in Vocaloid, easing the harshness they endure down below, and giving them an opportunity to move on from Vocaloid to something else if they desire. The lightning/thunder could be metaphorical for the electronic nature of everything - lightning flashes are also used to switch scenes numerous times.

The producers that separate from the group at the end likely represent those like Kenshi himself who left Vocaloid. (Or, while I really doubt it myself, they could refer to Powapowa-P and Samfree, notable producers who had passed away.)

The person with the flower at the end may represent a Vocaloid fan: they first swing around Miku, then a producer, representing how using Miku was originally what got you attention, but the actual producers have since come to the forefront. (Or at the very least, most earnest Vocaloid fans will eventually make that change in focus.)

The last line of "even as the wind blows" could metaphorically mean that Vocaloid carries on despite the winds of change. It's not super clear, but Miku seems to be walking toward two new producers waving at her at the end, showing how even those who move on from Vocaloid have new talent taking their place.

The cake castle shown from above at the end represents Miku's ten-year legacy as built by the producers who use her; when they celebrate her birthday, they're celebrating the Vocaloid history they've all made. Of course, when it's shown in the "fans' perspective," this cake just looks like a cake.