What they did instead is paying thousands of dollars for Twitter emojis and dishing out a few give-away events where you had to practically advertise for the game to enter. Were you guaranteed to get any reward? No.

Essentially, instead of even acknowledging the anniversary, they made players advertise their game.

They were also supposed to introduce a paid bundle with some cosmetic items alongside a free concert stream (the concert was pretty good). But that was after the anniversary. Keep the bundle in mind, however.

What did it lead to?

Thousands of outraged players flooded social media.
Their discord was spammed with "qiqi fallen" emote (one of the characters laying on her back with a blank stare).
Review bombing got to the point where even Google Classrooms became one of the casualties

I'm probably missing some other details, but this lasted for weeks.

After a long while of non-communication, the devs gave in and finally decided to give players something. This "something" turned out to be the bundle that was supposed to be paid content alongside some (read "very little") in-game resources. There was also another another giveaway event with, this time, guaranteed rewards. The rewards were, practically, you either get a scooter or one cent. Needless to say, it left a sour taste afterward.

Honestly, it felt like a slap in the face, but it was enough for the things to start calming down.

So far, even though they're still very stingy with any sort of rewards, they at least make sure to congratulate the players somehow and give something.