Big no. Also, when will kids realize that "flush" is bad.
There are two completely different issues with spacers you have to understand.
1) They create well, space, between your hub and your wheel. The stock studs are designed to be directly connected to the wheel and as such only provide a certain length of exposed screw to tighten in the lug nut. The main issue with spacers is that by putting in a buffer, they shrink this gap and can prevent the lug nuts from tightening completely (which is very unsafe). Subaru studs are often quoted at being only a mere 3mm longer than needed for the lugs meaning any more than 3mm spacers and your stuck studs are simply too short. You can get around this by lengthening the studs of your car to some extent. Thicker spacers often come with their own studs bored in and completely cover the factory studs. This creates a possible movement point between spacer and wheel which is generally why they're considered dangerous.
2) Spacers lower offset, just as you said. The total offset (whither you have a spacer or not) is what really has an effect on the handling. If you have a +50 wheel with a 2mm spacer vs a +48 wheel, they are effectively the same (assuming the lug nuts have room to get tightened correctly). In other words, the second issue is purely about not having enough offset, independent of how that is achieved. You can have too low offset from using spacers or just form buying wheels that lower your offset.
Now, the real question is what are the adverse effects of lowering offset? Basically what happens is the suspension of the car is designed for a certain moment arm (lever) for the wheel compared to the hub. The suspension is then designed around these constants. If you push the wheel further out, you will widen the stance of the car but you will also be lengthening the moment arm. The "scrub radius" is usually used to describe this angle and has a direct impact on the performance of your suspension. Small changes in offset will not have substantial effects but more extreme changes can see drastic handling changes. Cutting too much offset can ruin your turn in response in particular.
And 5mm won't do anything for looks, they will just make your effective offset even less ideal than it already is.