[Imp]

Try reading more books before you comment on real life.
Open terrain like you mentioned if the squad had any sense they would be dispersed and using bounding movement.
Close ambush in jungle or street cleaning according to you no one would advance ever in that sort of terrain because they would all be dead.
Vietnam they quickly found out if you want a successful ambush those first 2 kills better take out the men in command, you might get your result then otherwise it’s a close quarters fire fight.
A nutter hero type on either side could change the outcome, you want a defender look up the Gurka who lost an arm to a grenade and still took out 31 Japanese.
Attacker read about Kursk biggest tank battle ever lots of infantry to, it was the beginning of the end for Germany because they could not afford the losses but they somehow advanced for a while against prepared positions with impossible odds.