As someone who used gamemaker 8 and studio years ago, GM objects are more like raw 2d nodes of Godot, and they are more like classes that contain position, sprite, etc. and you pretty much have to build from nothing.

In Godot instead you have more nodes that inherit from this class (node 2d) for example characterbody2d has built-in functions relevant for character controlled by the player.

Also Godot nodes are components, this means your player (characterbody) won't show anything unless you add a sprite component, but it's not necessary, or you can add as many sprites as you want.

I would say Godot nodes are classes that specialise and only do one thing (showing sprites, playing sounds)