i always play games before rating them but mostly leave "generic comment" since i'm not smart at judging games
That is completely fine. I had a look at your timeline and while it is sort of generic you aren't copy pasting things and leaving dozens of comments.
There is no secret sauce for judging. The option of a novice is as valuable as that of a pro. In the industry your games will generally be played by people who have no idea what it takes to make a game. All they can tell you is if it was fun or not. In the jam it is your job as a rater to focus on things you have noticed and if you just can't find anything that could help the jammer improve it might be best to just move on to the next game.