As I recall the cast of prospects was significantly different at WR/TE in the 2019 training camp vs. '18. We'll just have to disagree about OTAs being a "joke" for the team leader needing to get in sync with new skill players while setting an example for everyone else. The offense's misfires in training camp were well documented, a problem that very well MIGHT have been helped by Brady attending OTAs like he did faithfully from 2000-2017. It wasn't Brady who needed the work, it was the passing offense under Brady's direction that needed it.
Every team handles scheme installation differently and OTAs can be integral to laying the conceptual foundation for newly signed players and rookies. In a passing offense as complex as New England's, Brady being onboard early with the new recruits could have had a positive ripple effect through training camp into the regular season. As for BB's part, there's not much he can say or do about Brady's choice regarding an officially voluntary function. Brady being miffed about his contract situation also might have been a factor.