I think that people are too harsh on this adaptation. I wouldn't say it's perfect, it's is definitely not. The adaption itself is the biggest problem in my opinion. But most themes the original musical touches on, are there. They even added a new one [spoiler](+ a new song) about medication and depression[/spoiler] which I thought was also very good. So I think storywise there is almost everything there.

Where it fell short was the directing and in some parts the script I think.
The film feels a little bit loose und somehow unstructured. The musical scenes are sometimes bland and doesn't always fit the music. But I have to admit, that this is also veeeery difficult with these songs.
The songs, while often having an upbeat instrumentation, always have a kind of sadness in them. And I think that "Waving through a window" with a dancing or choreographing Ben Platt would not have been better, at all. At least this way, the overall story and the acting isn't harmed by these musical numbers, because they are so focused on the text and the meaning.
I also didn't have a problem with Ben Platt even though he is a little too old for the role. His performance brought tears to my eyes several times. But that's maybe because I can relate to this real inner self he's hiding because he's afraid that people might not like him a lot.

Also, while Nik Dodani's performance was quite funny, the character lagged the small connection that Conner and he should have had, I think. He really wasn't a friend of Connor here.

Oh and the musical number of "You will be found" could have been the only number with a singing crowd I think. I really wanted to see a choir stepping in and sing this "anthem"! But they instead tried to recreate the way that the musical presented this song. That didn't translate well to the screen.

But overall... In the end, as I said, it brought tears to my eyes. I don't care if it was just the story or the performances and that a lot was bad like most people say. I felt all the things the characters sang about and... that's enough. ;)