Gale did feel a bit weak at levels 1-2, but his ice cantrip was still immensely useful and his fog and sleep spells were incredibly valuable in turning the tides of early fights even if he spent much of the time downed.
But at levels 3 and 4? He was an absolute monster doing massive AoE damage with Burning Hands, blasting whole groups off ledges with Thunder Wave, and just all around controlling the battlefield with Grease and Fog.
Once the wizard has a few spell slots to burn they really explode in raw power. Especially because there's currently no reason not to just long rest before every fight. And even if you don't exploit long rests between cantrips and their ample spell slots my wizards usually have more stamina than my other casters just because they can afford to drop a couple Burning Hands and still be fine for another battle or two.