Pressing the button enables all simulated power on the FSX runways with best friction values all the time and no dirt, moisture or other things simulated.

I you would switch from on-off buttons to e. g. pedals, you could alter this behavior somehow and make it more realistic. Currently, with the button, you are going digital with on-off braking. Hard to simulate a real reaction then.
I doubt that the real pilots jump on the pedals after touchdown like this key press simulates (going from 0 to 100% in milliseconds), so at least the beginning of the process would be far more gentle with pedals.

There might also be some addons around to simulate runway conditions.

Depending on the length of runway, pilots in 707 and even 727, used reversers and speedbrakes mainly and used pedal braking at the end of the landing roll, turning off the runway and tight turns and such..  Ease up on the reverse thrust also if landing on a long runway..  Today in real flying is different though, so much traffic, so little time and space... Touchdown, reverse, autobrakes and get the hell off the runway even at large airports and controllers tell you what taxiway to plan for on final if it's busy and it's usually one where you have to slam on the brakes.. That's why airliners today go thru brakes and tires like socks.. cheers