Cant log into Wordpress Admin after reinstalling a vps server with DirectAdmin

Most certainly not.
Depends on what php mode you use. But if you use mod_php than this could be the case, however in that case you should use mod_ruid2 for protection.
When using php-fpm normally 777 is almost never needed anymore.
They should just be 755.

That may point to some issue in the .htaccess file.