Yes, the Last time Russian space programm suffered casualty was in 1971 - parashute did not open in time and crew died on impact. I trust Souz spaceship more than any other, especially because my farther works as a fuel engineer other there
The main problem with Souz as a major transport is not safety but its limited capacity - 3 people and no more than 2.5 tons of cargo. Shuttle can carry 7 people and up to 50 tons,IIRC.
Saturn V was not that powerfull, it could carry about 100 tons on low Earth orbit. The Russian rocket Energia, wich was designed for spaceshuttle Buran could carry 150 tons. Too bad the programm was canceled because of money.
Still, it would require several launches to assemble ISS.