Are the cleric and druid spell lists separate for purely thematic reasons, or due to other balancing factors in the class designs?

Question

I'm considering a lazy approach to creating a Power of Nature Sorcerous Origin simply by swapping "druid spell list" in for "cleric spell list" in the Divine Magic class feature of the Divine Soul sorcerer subclass from Xanathar's Guide, and giving the other features nature-themed flavor text. (I'll also replace the automatic initial spell as thematically appropriate, but I'm not worried about that since it's just one spell.)

Are there balance concerns with doing so? Is the cleric list significantly more or less powerful overall than the druid list, possibly because of other class design features (e.g., perhaps druid is designed to lean more on Wild Shape and therefore has reduced spell power), or is the difference really mostly flavor, to make sure druids have a distinct nature focus?

Answer 1

From DMG p287 (Creating New Character Options)

Changing Spell Lists
Modifying a class's spell list usually has little effect on a character's power but can change the flavor of a class significantly. ... Be cautious when changing the warlock spell list. ...

Based on the above comment from the DMG, it would likely not be a significant balance issue to swap in the druid spell list and swap out the cleric spell list.

Note: I've kept the cautionionary clause regarding warlocks to preserve that caution and suggest further reading for any curious readers.