Not considering magic, druids are probably more likely to live and thrive with a balanced diet.

Getting enough food for a plant-based diet that would be satisfying and healthy, requires either hectars of unnaturally prepared land, or several hours of forarging.

The druid would have to take the animal population into account, both for food in regards to forarging, the nature around them, the earth, etc. They would have to consider the ecosystem overall. If they compete with animals for food, then there may not be enough food for both, and either will die. Humans are adapable in terms of places to live, many animals are not, so this means moving to another location, or accept that a balance must be struck, the latter very likely in the druid's case.

Killing animals can destroy ecosystems, not killing animals can also destroy ecosystems.

You must find balance.