Making an entire level in just 3D mode only doesn’t feel very intuitive. Is there no 2D map mode similar to the various Quake level editors like radiant/jackhammer/trenchbroom etc?
I’m not familiar with the tools you are referring to, however:
In Scene View there is a 2D button:
Also, you can use this gizmo in the top right of the scene view to switch to any of the six “cube” face views of the scene, and change the projection from perspective to Isometric with the gizmo right below it:
Finally, under Window → Layout you can switch to 4-Split mode which shows three isometric views (top. from, right) and one perspective view.
That isn’t really what I’m talking about. I mean stuff like this:
Note the 2D grid views. Unreal engine also has something similar to this. But why doesn’t Unity? It’s a considerable pain being limited to working in raw 3D mode only.