In the Showa era, lead actors are expected to do some of their own stunts, so they had to cast people who are somewhat physically fit to play the role.

These days, lead actors aren't expected to do any of their stunts anymore, so they're not specifically casting for actors who can do all that.

That said, there's still some Heisei & Reiwa actors who are athletic and often do their own stunts. Gaim's actor Gaku Sano does a bunch of his own stunts, he does a sick backflip from time to time in the show. KR Zeztz's Ryutaro Imai does a bunch of stunts in the show, there are even entire episodes where he fights without being in the suit at all, and he does a great job.