In AVABEL CLASSIC, you can freely attack to any enemies with skill shortcut that is set with skill icon.

The default setting is set to "Assist" to help you attack nearby monsters.
You can change the setting from below:
"MENU" -> "Options" -> "Config" -> "Control" -> Toggle "Battle style"

Additionally, if you use "Auto function," it will automatically attack with skill short cut that is already set to target enemy.