Where I disagreed with you was your apparent belief that the subsequent Phillies games shouldn't have been cancelled. But having screwed up with the Marlins three times (by letting them play Friday, Saturday and Sunday) they are now taking a much more conservative approach. And the fact that the Phillies had two positive tests yesterday suggests they were correct to not let the Phillies play or practice.
Now they are saying they might still let the Cardinals and Brewers play tomorrow if the outbreak is confined to a few players, which seems wrong.
Bad as MLB is, it's not surprising they are making it up as they go along because everyone has been, even our best scientists. Nobody really knows if the protocols and definition of "close contact" are sufficient, or if guidelines that apply in normal life (both outdoors and indoors) apply to baseball.
I think the Original Sin is twofold: 1) Being more focused on money than safety, as they wasted so much time on CBA/compensation when they could have had more runway to get this season played and 2) Not figuring out a modified bubble system - which was also about money, as the teams still have more TV and signage revenue streams being in their home parks, even without fans.
I think it was always clear that they didn't care/expected something like this to happen. If they actually play a season and 2-4 teams aren't participating, or if 2-10 teams are barely competitive, they will probably have to come up with some kind of draft pick compensation (in addition to all the other teams or the league making payroll).
Of course the real Original Sin is just trying to play, You can't expect things to go normally or well. MLS and NWSL worked because the minute a team had an outbreak their season was ended. Shutting down a team for 10-14 days is de facto the same thing so maybe that should have been the plan all along (and if they'd done it to the Marlins on Friday maybe it wouldn't have happened to the Phillies... yet).