I largely agree.  I kept waiting for a twist or some sort of reveal, but none ever came.   At least not one that was big enough to justify the length this cover story.   If this was just Oda trying to keep part of the story fairly "light" in order to contrast the events of Elbaph and God Valley, then Yamato's story should have been either funnier or cuter or SOMETHING.    There should have been more fun "antics", if this was just a moment of comic relief, it should have been a bit more light.  As it stands, it feels rather bloated.
Part of me even kind of wonders if this was Oda trolling the fans, a little.  Oda seemed to have put a lot of thought and effort into designing Wano.  And a lot of fans reacted by saying they thought the arc was overly long and bloated.   So, maybe Oda just wanted to take a poke at those guys.   "You don't like Wano...well how about EVEN MORE WANO, how do you like that?!  CHOKE ON IT!"   I don't know if Oda would be that petty.  But...I could almost see it.   We might have gotten "Wano Act 4" just to spite the critics of the arc.
But, just to play Oda's advocate, for the sake of argument...
I suppose you could say that Oda just wanted to use all the notes about Wano that he created, but never got a chance to use in the Wano Arc proper.   Oda seemed to do a LOT of world-building making Wano.  Moreso than most islands.   Wano has a lot of districts and features we never got around to seeing.  And this cover story gave Oda a chance to show off every region of Wano that probably only existed in his notes up until now.   We did get to explore every region, and see what makes each area different from each other.   We got to see the Scabbards ruling these areas, and how everything's improved.  If you actually enjoy Wano, then this actually helped flesh out the region even more than before. 
The problem is that Wano...is basically just Japan.  And while I really do like Japan, it's a little "plain" compared to some of the more over-the-top islands we've seen in the One Piece World.   Wano comes across as a little "bland" as a setting, because it's a fairly "realistic" land, in a world where a lot of fantastical set pieces are all over the place.   But, I can't deny, Oda put a lot of thought and effort into designing this island.   Chances are, Oda just wanted to show off all the background work he put into designing this place.
But, there's also Yamato's pilgrimage.  And I think this is more of a metaphorical element for Oda himself.   Oda was using Yamato's pilgrimage as a sort of "journey of spiritual cleansing" for himself.   In Japan, it's sometimes traditional to go on a long journey visiting various shrines, in order to cleanse your soul and ready it for the challenges ahead.   Like a samurai preparing themselves for a big upcoming battle.   Like, taking a journey across the Kumano Kodo Trail.
https://en.wikipedia.org/wiki/Kumano_Kodō
https://www.nationalgeographic.com/...mano-kodo-japans-most-sacred-pilgrimage-trail
https://www.ageist.com/travel/pilgrimage-of-transformation-on-the-kumano-kodo-trail/
So, I think in a way, Yamato's journey on the cover story was Oda symbolically preparing himself for going into the Final War.   From everything we've seen on Elbaph, we'll probably be entering the Final War Arc after Elbaph is over.   Oda drew Yamato going on a peaceful pilgrimage to various shrines and locations, in order to cleanse his own soul, and to prepare himself for drawing what will likely be the final major arc of One Piece.   It's a way to "center" himself, before the big challenge ahead.   Preparing himself for drawing the grand finale that he's been building up to for decades.
...Or maybe it's not that deep, and Oda just really likes Wano.   He does seem really fond of the place.   He might have just enjoyed spending more time there.
So, yes, I think Oda may have lingered on Wano for a bit too long.  But, if he was having Yamato go on a long journey, in order to prepare himself for the end of his magnum opus, I really can't blame him.   He may have been feeling a bit sentimental.   And maybe he's still not quite ready to say goodbye to the story he's spent most of his life telling.   Because now that the Yamato cover story is over, we may be close to finally entering the true final era of One Piece.   I can't blame him for lingering for a bit, before he shuts off the lights.