Assuming "nodeList" is an array on the gdscript side, then when you use Get() to access it you will receive a Godot.Collections.Array object.
Godot arrays can contain multiple types, so each element is an object.
The easiest way I see to convert a Godot.Collections.Array of objects into a list of Vector2 is:
Godot.Collections.Array nodeList = (Godot.Collections.Array)maze.Get("nodeList");
List<Vector2> vectors = new List<Vector2>();
foreach(var i in nodeList)
{
vectors.Add((Vector2)i);
}