Spider-Man: Far From Home - 5 Reasons Why The Twist Ending Was A Great Idea (And 5 It Wasn't)
3. Not Great: Makes MJ's Deduction Of Peter's Identity Less Meaningful
Far From Home's setting up of the relationship between Peter and MJ was brilliant, the latter's deduction of the former's true reason for always sneaking off being a pretty integral part of this.
So, telling literally the entire world that Peter Parker is Spider-Man kind of removes how impressive MJ's deduction was - it somewhat diminishing the special nature of the pair's relationship.
It may be a small consequence of making Spider-Man's identity public, but one that could have surprisingly large effects in the future, with it perhaps meaning that a fully formed relationship between MJ and Peter could be delayed - due simply to how it diminishes the aforementioned special nature of their dynamic.
Basically, if everyone knows, what difference does it make if someone knew slightly earlier?