Generally speaking, it all depends on how the platform secures their passwords. If they encrypt/decrypt it's more important to have a unique password as it's only secure until the platform gets hacked, at which point your password will be leaked.
I think most sites use some form of hashing today tho, this means you'll have brute force protection from the platform most likely, but only until it gets hacked. Then you'll have to reply on the hashing algorithm being a secure one, like bcrypt or blowfish maybe. SHA256 is weak but common, if it's md5 or similar it's broken and you'll need a unique password.
But generally for hashing, length is way more important than special symbols. You're more likely to get hacked by a brute forcing robot, than someone you might know sitting there and trying to guess your password manually. Look into passphrases if you can. 99Stack Cloud supports up to 4096 characters for password for instance, why not use a whole sentence, with words you can easily remember. This will give a great length and become almost impossible to brute force.