This sounds seems a little bugged out (no pun intended). It seems unnecessarily loud.

Honestly, I'm just bad at sound effects. I found this on a website for royalty free sounds, and slightly edited it in Audacity, but I have no idea how to make it sound good. I know this isn't a very satisfying answer, but I can't really make it work. The best solution would probably be for me to remove the sound but I don't know if it would be better for them to be silent.

What about this

https://soundbible.com/1322-Butterfly.html

Mine in 1.19 doesn't make any sounds. On my server, when we get close to a butterfly, it actually crashes the game and says Error packet 93 and then tells us a sound is missing.

The way it is in my current game, is that the sound of butterflies is way to loud compared to other sounds. It's not that bad tbh, but the amount of sounds and the volume is kinda annoying.