Universal designated hitter
While the American League adopted the DH rule in 1973, pitchers have continued to hit in games played at National League ballparks. That won't be the case in 2020, as both leagues will use the DH to avoid overtaxing pitchers by having them hit.
Some how Designated Hitter was a side of effect of COVID.
https://www.mlb.com/news/mlb-rule-changes-for-2020