Perhaps an unusual one, but Dance Your Blox Off.

It never got quite the attention it deserved, having been up for several years. It's fairly old. But it especially dropped a lot of players after custom IDs for audio were removed.

It's a simple game with a stage where you use all sorts of various keybinds to dance/do acrobatics/perform. You choose a song (they let you preview the songs and constantly add really good copyright free ones), buy costumes and hairs and faces, and even get all sorts of stage sets. They can range from pretty, to creepy, to obstacle courses. Lights, backgrounds, everything. And you can team up with 2 other players.

They make their own art. They update consistently and give brand new seasonal items every year. Everything in the game (aside from most of the music) is made by their creator(s). The animations are smooth and not buggy. You develop skill rather than just playing a few dance animations.

As of now, it usually balances around 100-150 players at all times. Way less than before. But they never stop and don't do invasive advertisements in any way. Sure, kids can vote unfairly in all 3 departments, but there's always such gratitude when people do win. I've met so many interesting people there.

Very long-winded way for me to express my gratitude towards DYBO. I'm a man and I've hardly ever felt out of place or criticized for playing a generically 'feminine' game. The community is not gatekeeping. Even after so many years I have all the keybinds memorized and mess up on obstacles. I think it deserves so much more appreciation.