Standalone game's built version is zoomed in at most resolutions. Looks fine in game view.

I built my first game successfully and when I finally opened the game I realized that in most resolutions my game objects had been awkwardly zoomed.

Now, in the game view, I kept the aspect ratio of a standalone game screen and everything looks fine there. When I build the game and open it in any 512x384, everything is awkwardly scaled.

I use Unity 2017.3 and while looking through the forums all the answers I could see were for unity 4/5 and from pre-2015, which I assume is relevant as Unity must have changed a lot.
Note: In the images provided, everything is a UI game object, apart from the Unity logo which is a raw image.

Imaged attached as refference:

Fixed by deleting the empty game objects I had which I used to store menu items. I had turned on root canvases scaler but it had no effect. So I created non-root canvases inside my main canvas and used those to store my objects instead. Then I was able to use anchor points and the canvas scaler successfully.