Yes, most people were physically tougher in the past than they are today.
Simply because in the past, people did hard physical labor all day, everyday.
But that doesn't mean today's people cannot be just as physically tough, just that most have never had to be.
I read a quote from a british SAS officer that sums it up nicely.
He said; , after WW ll, the sas had no problem finding soldiers who were physically tough enough to be in the sas, we had problems finding people who were smart enough.
Now, we have no problem finding soldiers who are smart enough, but we have to teach the soldiers that they can do three times as much physically as they think they can and they can keep functioning with extreme levels of physical abuse.
2. There is no comparison between elite soldiers today like Delta, seals, sas and past soldiers like knights templar.
Today's elite soldiers are far stronger , have far more endurance and are far smarter.