This film is uneven, though worth watching for it's complex take on teenage developmental social anxieties and needs. I think many reviewers are bothered by the film because of it's sympathy for what many consider to be the utterly immoral main character. But in real life, people's choices, especially the bad ones, ARE motivated by conflicting needs and motivations and few people have an unwavering moral compass, in spite of what many under the age of 25 prefer to believe.
Ben Platt is perfect in that role, he IS Evan Hansen, as he was on Broadway and the fact that he does not look 17 is of no consequence. The obsession with an actor looking the real age of their film character is puzzling. This is hardly the only thing "not real" about what we are seeing! People don't break out into song in the middle of their dinner parties either.
Main criticism - it is too too long. About 30 minutes should have been edited out, especially in the second half of the film.