Not all spellcasters can cast ritually, this is an additional feature some of them have. Look for it in the class description after "spellcasting". Bards have such a feature, so if one were to learn identify, they could cast it (if they have the material component).
The Ritual Caster feat has multiple advantages:
- The character does not have to be a spellcaster to take it. Even a
fighter can choose it and learn spells.
- If you choose a spellcasting class you have levels in, you can cast all ritual spells you already know as rituals.
- You can add spells to your ritual book. Most classes only earn spells when they level up, with this you can have more spells.