They're skipping too much story.
It's a pretty daring choice to timeskip the entire duration of the penalty, but there's still plenty of material for the author to work with. Those first 100 chapters were like 2 months. I am a bit surprised he skipped the potential "2nd years accepting Shotaro" arc, but it's also pretty smart given that you can see all the problems with the situation from the outset (why did we suffer this much just to have a 1st year captain, where's the respect we will eventually be owed) and resolving them is just a matter of following the path to its logical conclusion (I still want to play baseball so I'll stick around, Kano's not a bad captain, the fact we were even in that situation to begin with was the real problem).
Would it add that much to the narrative to have it all play out? Dunno. Lots of writing is a compromise, and if you're going to compromise on a part of the writing in a sports manga it might as well be the bit where they're not doing anything.