Every fight had a purpose, GB was another hype for Shanks (and of course for the movie), BB in Amazon lily seemed pointless at first but this brought to Garp vs Beehive, guess maybe it could be considered the same for BB vs Ace. The difference is that the fight was indeed a skirmish which was resolved in a few panels.
All that is happening in Egg head is just the arc build up, it happened in Wano with Zoro vs Killer, Luffy vs Kaido and so on.. the fights were needed to make the CP0 guys allies and the seraphim were there to stall and actually just to see them do stuff amd show their powers is enough, I doubt they will be beaten just because they are kids.
Also Oda doesn't go heavy on fights now even because Wano just ended and we had what?... 20 chapters or more of only fights? I don't know the exact number but if you count rooftop fight, SHs vs Kaido captains, Law and Kidd vs BM and Luffy vs Kaido you probably have way more than that, so it is right to not go in fight overdose, not everybody here is a vs fanatic, luckily. But actually it seems people now is enjoying OP way more than during Wano, I have seen anybody complain, so it seems the formula is good.