On the contrary, IR penetrates past the dermis. Also, IR is much much higher energy than microwaves although both are non-ionizing radiation and will only result in heating. The amount of heating you get from the sun spread over a square meter is close enough to the power output of a microwave. Even with the lower attenuation to 2.4GHz vs 240THz the peak heating is still occurring on the surface. You'll probably notice if you're being heated with a couple hundred watts of power. If you don't notice then you're absorbing so little power that there's no chance of any injury. You'd need to raise the temperature of your organs by at least 10 degrees to cause any organ damage and your skin temperature would be so high by that point that you'd already have burns and any sane person will instinctively move away from the heat source causing them pain.

It would take far too long to heat up hot enough to cause more than skin burns and nobody would ever stand there long enough to even get a skin burn to begin with. Any sink presents a much more serious risk of injury than a broken microwave. A hair dryer is more dangerous.

It seems like you might be extrapolating the speed of heating some piece of food and assuming it could possibly heat someone outside of the microwave at the same rate. It can't. The only reason small things heat up quickly is because in a closed microwave the walls reflect the microwave energy many many times before it's eventually absorbed by the food. It's a high Q factor resonant chamber. Effectively when there's little energy being absorbed or escaping the intensity of the microwave radiation is multiplied many times over until the energy being absorbed is equal to the energy being put in. If the door is removed it's just going to bounce out and you get none of the massive jump in intensity that you get with the door closed and only a small 1/2 lb of food inside.