I personally still think Juventus have had a good squad in the Allegri era, especially when Juventus managed to bring in Vlahovic from Fiorentina and also Milik from Marseille. But unfortunately, Allegri failed to make Juventus better, and also the case that befell Juventus might make him also fail to focus on improving Juventus performance in his coaching era. Because anyway, when Vlahovic and Milik were successfully obtained by Juventus, at least many observers also predicted that Juventus would be able to get the Scudetto at that time.
But anyway, what happened Juventus still failed and entered the next season Juventus also managed to appoint Thiago Motta to be the head coach of Juventus. Of course, with Thiago Motta's success in making Bologna have good results last season will be a great hope that Thiago Motta will also succeed in making Juventus back into a team that has dominance in Serie A. Because after all, basically Juventus already has players with great potential and thus, it should not be difficult for Thiago Motta to make Juventus better.
Yes, I also think that Allegri didn't do too much harm, in fact I don't understand all the accusations rained down on him. We had many misfortunes, punishments, injuries and in any case he kept the team going. In my opinion he was treated too badly by everyone and he didn't deserve it.
Now I hope Thiago Motta makes fireworks!
I would say that you are both right and wrong. I think he was worthy of getting sacked, Motta seems like a better manager so when you find a better manager, you end up sacking your current one and getting a new one. That is the part where you are wrong, he wasn't good enough to keep the job, he wasn't good enough, and him leaving is fine, I agree with that part.
However, what I agree with is the fact that he was "attacked" too much, from fans, from media, from social media, even from management. He didn't deserve that much neither, it has to be something in between, like "we thank Allegri for all he did, and we wish him the best in the future" type of parting ways. If they did that, then it would have been a lot better and we wouldn't really face any issues.
In the end, he is gone, and Motta is here, so they should learn from their mistakes and shouldn't treat Motta this way as well, keep him happy because he is your manager. Just constantly complaining and whining about the manager doesn't make anything better, a manager seeing all of those doesn't suddenly become better, just cheer him on, and tell him you expect great things and he will be hyped and happy, which will make him win more games.