How to write interesting non-tragic characters?

Hey there, this is my first post in this sub. I'm a young non-native English writer who hopes to write a short story in English. My favorite part in crafting any story is writing characters, especially female ones. I'm not a professional writer or anything but writing has always been enjoyable to me.

One thing that my brother pointed out though, is that all my characters have tragic backstories. I've always written characters with such backstories because i felt that they'd make the readers more immersed and emotionally invested in the character. But often ended up making stories too dark to the point that even i felt that i overdid it.

I'm still learning and trying to improve my languague but i'd like to know how it's impossible to write interesting characters that aren't tragic. I often worry that a character who doesn't have a complicated backstory may seem boring or uniteresting.

So ... Any advice is appreciated, thanks in advance