For me, the show from 1-12 is perfect. Great cat and mouse games with zeon and white base. Most of the teens are great too, but lulls a bit. There are great episodes but a few redundant ones as well.
Once they get to jaburo it picks back up again. Then once theyre in space the rest of the show is amazing.
This is actually one of the Gundam tropes I've noticed that I don't really like. Seems like a lot of the series open up this way, with battle after battle every episode. I find it a little boring, everything always picks up when the show slows down a bit and they introduce more of the bigger story into the picture.
Not to say I hate those early parts but it's hard to keep super engaged when it's just fight fight fight.