So I don't have a problem with his immaturity because they seem to be going somewhere with it. He's obviously still alive (which is annoying without an escape scene like Vader had from the Death Star) if they show his training it could effectively develop his character.

But it's annoying he was so easily defeated when they established him with threatening new force abilities, freezing a blaster bolt is badass and makes perfect sense. I think his mind reading was new to the films too, but I might be wrong. It makes his subsequent characterisation and defeat mismatched to his abilities. Also his dark/light side inner conflict seemed super simplified, we also see this with Finn compared to the other Stormtroopers.

Also the new Tarkin being so young weirdly seemed to emphasize the youth related weaknesses in Ren's character. Do you not have to rise up the ranks in the First Order? Did he get his position for his speeches? Wouldn't it be cooler to have an old Imperial officer with experience to clash with Ren, and be ruthless to the good guys while Ren does his training.

It was between very good and great overall. I just hope they do something really new with the next one.