By default, there are limited ways for characters in D&D 5E to cast ritual-tagged spells as rituals. Either they choose a class with the Ritual Casting feature, choose warlock with the Book of Ancient Secrets invocation, or choose the Ritual Caster feat.
I'm considering a house rule that gives this benefit to any spellcaster. The rule would create some overlap between classes, adding some utility to a wider variety of party combinations (e.g., parties with a Sorcerer instead of a Wizard). The wording would be something like the following:
If a feature lets you cast a spell that has the ritual tag, then you can cast that spell as a ritual.
This rule should apply to ritual-tagged spells gained through a class, subclass, racial feature, or any other feature. It could also apply to spellcasting NPCs. But it should not apply to spells cast through scrolls or other items.
While this rule benefits some (sub)classes but not others, thereby shifting the relative power balance between classes, that is intentional. For example, this change adds versatility to Rangers and Eldritch Knights, yet it should not let them overpower Druids and Wizards, respectively.
My main concern is about mechanical choices that would significantly boost the character or party beyond what's expected for their level, such as somehow exploiting Magic Initiate to gain something much stronger than an ASI or feat.
So far I've considered possible consequences, and can't find ways it could unbalance or break the game. Am I missing anything? What possible exploits, if any, could be caused by this house rule?