They spot you if you're exposed. Hide and you're good.
There is a mechanic to show you visibility to enemies, just find the right hack
You can Zoom in/out with the scanner. You can't if you're scanning but move it a bit upwards (to the sky for example) and suddenly you can zoom.
So, no it's not disappointing as hundreds of other things people are reporting (because it's cool to hate on the game?) - you just have to read more and I guess.. play better.
Good luck!