The random/free fireworks boxes have an unfortunately excessively poor RNG. Using the entire week's fireworks packs should be just enough to let most players finish the free aspect of the event. This is not a change however, it has always been this way.
The purchased ones, though still highly variable, are at least better. Hopefully this clears it up.
Also, for what it's worth, while the drop rates on these are poor, I think you have just been getting unlucky. Here is my drop for this week.
As you can see, it's not all 5- and 10-point fireworks, so you have just been getting unlucky. This happens when you have a very small sample size. Hope this helps!
P.S. I have extra packs leftover from not using them during the Tsunade Young Adult week because I didn't care about her. xD
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