Well lets look at Shadow Replication a sec.

It only took Naruto 1 day to learn it and apparently Shikamaru's family has a "thing" for Shadow jutsus, yet he doesn't even know Shadow Replication, which would take an uber-genius even less time to learn than Naruto, specially since Naruto was a lot weaker back then than he is now.

You'll counter this arguement with the idea that the Shadow Replication jutsu is a "forbidden" technique, but wtf is that supposed to mean? Naruto and Kakashi both have used it, Naruto using it all the time, what's so forbidden about it? Maybe it's forbidden cause it's such an awesome technique that takes so little time to learn?

I understand that Rasengan/Chidori would take a long time to learn, but I'm not asking for an uber-leet jutsu for all the non-main characters, just a 1 or 2 new ones, they could suck for all I care, long as it makes their fights more entertaining to watch.

Main reason why the creators don't want Shikamaru to know Shadow Replication at this time? Forbidden Technique is just an excuse to let Naruto use it all the time, making it look like his own unique thing he does. If they let Shikamaru do it also, it'd take away from the "specialness" that is Naruto, the main character.

But I seriously would prefer more interaction/background on the other characters than Naruto/Sasuke. We've known their story since the beginning, we can guess the outcome of their battles an episode ahead of when they happen.

Main reason I really don't like PVP in most MMORPGS? Same reason, you can guess the outcome of the battle before it even starts.

It's a lot more fun/interesting to see other characters battle it out with multiple jutsus that you haven't seen 50 times before. It might not be "realistic" in the world of Naruto to know more than 1 unique jutsu as a genin, but this story isn't exactly supposed to be realistic, it's supposed to be entertaining.