Well its all up to what you think.
Personally I think its obvious that "Before and After" is a better written, more adventurous, more original, more meaningful and better acted episode than "Favorite Son" so its quite difficult to swallow that it has the same score.
I guess you found all the bits with Kes and her family/the crew uncovering the mystery behind her jumping backwards in time fairly boring. If Kes doesn't hold your attention then its understandable that you wouldn't enjoy the episode. Everyone has their own preferences, I find Kes to be a very watchable character and thought Lien turned in her best acting performance in this episode being particularly good at acting as the confused older version of herself. The only bit where the episode lags is during the present day when there's a tad too much technobabble.
But overall seeing an alternate future of Voyager where the crew have been through a lot of changes and Harry has married Paris's daughter (!) and Janeway and B'Ellana were dead was really interesting. Not to mention the action of the "Year of Hell" segments and the urgency of the later segments where Kes is running out of time to save herself.
But if you believe that it really only deserves a score of 4 then give it a 4. You might change your mind if you rewatch it like I've done with several episodes I've previously disliked, and you might not. Everyone's different.