Neither Binho and Matri subs did make sense; especially, Matri. it is not because he is Allegri's ideal one; however, it is because we did not sent/cross any ball inside the area before or after Matri came in so he can be effective; therefore making his presence a complete eyesore.
I would argue the Robinho sub does make sense, as any support forward coming on to try and exploit late game lapses makes sense. Additionally Matri's worth isn't limited to crosses, if nothing else, him occupying the CBs in the box leaves space for the other forwards to shoot. Clearly the execution was lacking but both players fulfilled their bit-part roles.
Regarding Abate, I don't think he is a bad player but last night he played bad and Lazio were happy not to press him. When Constant is playing, you would normally see the ball pass through his side because he is the weakness. The problem is that our midfield is too slow (Muntari and Montolivo) in moving the ball forward and are very uncreative between themselves so the outlet becomes the full backs who then concede the space behind them and our CBs are not reliable enough to cover properly every time.
Agreed Abate is not a bad player, but he's not a smart player at least in the attacking sense. This isn't anything new, it was just magnified this game because he did very little right.
I'm a little unsure about the bolded sentence whether you're referring to Constant's defending in comparison to Abate, if so, I have no issue with Abate's defending. I'd be very happy if that were his only job and Constant/De Sciglio be allowed to contribute offensively to the same degree Abate does rather than the current opposite.
The speed with which Muntari/Montolivo move the ball forward doesn't seem a causality for using full backs in attack. It's a matter of negating numerical advantage, even the best teams use many numbers in attack to keep every defender accountable. Furthermore speedy play is typically restricted to counter attacking which Milan do within games but not as their mane style. So again, high numbers are used, now to minimise lack of creativity.
However, with many numbers forward it will leave the CBs exposed if the ball is lost, therefore it is the responsibility of these same players to return as quickly as possible or delay the opponent's attack by pressing. It was effective in this game and meant any covering Zap/Zac had to do was painless.
Basically the team is so horribly assembled that one weakness can exploit all the other weaknesses on the team and that is why we are conceding on the most avoidable of situations.
Horribly assembled is harsh, Zapata is a weakness when he holds the ball too long, Constant has been a weakness but his time will decline. I think a key weakness is de Jong at anchor instead of Montolivo but de Jong was excellent and Montolivo also had a good game, so I don't see their roles changing and maybe Montolivo will come to relish the additional freedom he has as RCM.