I don't think it needed to be longer, he had plenty of time to clarify the story he just choose not to : /
It is super funny, and the comedy is why I loved the journey so much, something similar to One Piece (the style of humour isn't similar just the fact they're both very funny), One Piece is actually a great comparison I think just as I write this now.
One Piece has a lot of goofy and fun antics, but Oda packs it full of a fantastic plot that all connects together and is gradually revealed over time. I was probably around 17 years old when I first read about Solaria and thought that was awesome, I waited for 10 years to find more out about the civilisation Kabapu and Il Palazzo were from and he just ditched that : /
I actually think it might even be a Japanese thing maybe? To hint on that cool idea but then abandon it for more goofy antics instead.
As I say I still hold Excel Saga in super high regard, but I was bitter when I read the last chapter and I'm still bitter now, that instead of giving us more info on the history he hinted at, he did the Holy Brownie thing which as an Excel Saga reader you had no knowledge of. And even with the Internet I still don't fully understand what happened at the end. I haven't re-read the chapter since then, I must do that to see if it helps.