It's similar to the knocks on UConn's titles: "UConn killed everybody, which means college basketball teams suck, which means UConn's titles aren't that impressive."
Yes, every team has injuries. (See Porzingis, Kristaps.) But we're now beating a team that whooped on the team that took the defending champion's (and MVP's) lunch money. Half the world picked the Mavs. The Celtics were facing "the greatest offensive back court in NBA history." But now that the Celtics are up 3-0, it's only because Luka's banged up?
All you can do is just blow by everybody, ignore the chirping, and enjoy the title. (One win away.)