I mean one of the big ones is that WWI was atrocious for infantry because the tactics were 19th century, but the weapons were 20th century. IE generals were fighting the war like there weren't machines guns, chemical weapons and a laundry list of revolutionary developments that made outdated tactics just devastating.

A lot of wars have been fought since then and our tactics have adjusted quite a bit. Which means we're generally not sending wave after wave of men into entrenched enemy fortifications and railing about their cowardice when those assaults fail or saluting their "heroism" when those units are wiped out to the man.

We've got better protection and better medical care leading to higher survivability. We're not in a state of total war, and we're not anywhere near close to talking about lost generations from current conflicts.

Probably most of the posh people you know came back whole. Well that didn't always happen and amount of risk certainly tempers many peoples decisions about whether to serve in the military if they have options.

And frankly given a choice between serving in the darkest days of WW1 and a current conflict wouldn't be a tough choice for many soldiers.