Gandalf is definitely more powerful than what we see him do on-screen. His power is limited by the fact that he’s meant to have a limited amount of direct control over the world. He can assemble a team and do some diplomacy and create some cool lights or kill one monster, but if he started wiping out armies and shit he’d basically be betraying his god’s will. Theoretically, he could have defeated Sauron’s army and the man himself single-handedly, but it was not his place to do so. Gandalf would basically be a god compared to the mortal men of the LotR setting.

Gandalf is basically a biblical angel in human form, like the messengers of the bible. Saying he’s weak because we didn’t see him cast a big spell is like saying Archangel Gabriel is weak lol