Side effect? No that's real shit, brought to maximum like Roger Vs Whitebeard no one could even get close on an entire island. Now if you are saying that the fight isn't spectacular to see it's one thing, but not that the forces at play aren't enormous.
Yes, the sky splitting does no damage nor is it a move you can use against another opponent hence it's just a side effect
Roger and WB didn't split the sky, their adv CoC was just beastly enough to create a huge shockwave when clashing
Wich is what am talking about, just a clash between Roger and WB is leagues ahead of any confrontation between Kaido and Luffy, neither Roger nor WB was being serious in that clash, yet we're supposed to believe we're seeing peak strength in Kaido vs Luffy and their pitiful and basic clashes lmao
the fight will escalate to way more than this