Scaife couldn't block well either. Walker is probably the best TE we ever had as far as blocking and catching. Smith wasn't a "great" blocker either. So you have a long line of TEs who were far better pass catchers than blockers (Wycheck, Scaife, Cook and now maybe Firkser) and guys who know know Firkser has a special skill set for getting open and great hands. Plus we are a zone running team, not a power team so we don't need a bull dozer at TE in the run game as in the past (Mularkey all the way back to Eddie George).
And by the way Firkser had as good or better of a run blocking grade per PFF as Smith and Swaim. Swaim did have 26 catches for Dallas in 2018 starting 9 games so apparently he has something besides fins for hands.
(2) Geoff Swaim ultimate highlights - YouTube