To be honest, 500x500px pfps are just kinda blurry. I just wonder why Scratch puts their max to that, I wish Scratch made pfp available to set more than 500x500.

There's a method. I forgot though. someone link it

It takes up too much storage space, probably. To be honest, I don't see the point in having clearer profile pictures.

Use ezgif to convert pfp to webp file and upload to scratch