I think the biggest problem with how the wave system works is the giant disconnect between how manufacturers populate them and how retailers order them.
Manufacturers like Hasbro want to evenly space out their product over the course of a year. They'll have three or four waves a year, roughly equally spaced out, and usually with the wave contents equally distributed (with instances of shortpacking being particularly notable).
Meanwhile, retailers want to order a bunch of new product for their post-holiday reset, then just replenish their shelves as needed. They don't care what particular items are in a case of Product X, just that it moves from their shelves to consumers' hands as quickly as possible while making them some money through the use of their space and distribution systems.
I think the only real solution to this is for manufacturers to bite the bullet and upend their way of doing things to better align with retail. Instead of sprinkling their new stuff evenly throughout the year, front-load the first wave of the year with most of the new product. E.g., instead of four new Deluxes shipping in wave 1 with two of each per box of eight, make it eight single-packed figures. Maybe double up one one or two of them if they're expected to sell significantly better than the others. Then later waves that get fewer orders could be something like two figures at four per package. Or maybe four of a single new figure, and fill out the rest of the case with a couple package refreshes.
I don't know if this is feasible from the manufacturer side of things. It would require them to front-load all their design, manufacturing, and shipping operations to have the bulk of their offerings all ready to go at one time. That would be a huge shakeup, and there would undoubtedly be a big learning curve with some very costly issues. But the wind-up would be that they could potentially better align how many of each figure they're producing with how many of each customers want to buy without having the retailer as a huge choke point in the middle.
The bigger question might be, with the rise of online shopping and the demise of brick & mortar retail, would any of that be worth the effort at this point?
We're actually starting to see that crop up, in some segments.
The problem is the contrarian actions of many retailers, particularly, Walmart. Modern "waves" were pushed by retailers as an incentive to keep customers coming back. But with changing consumer habits...I'm not sure that is necessary anymore. Kids, in general, don't get as much as frequently as we did thanks to a myriad of other distractions. Collectors are primarily where the plastic addiction has settled, but it seems like a frequent refresh of product isn't really driving much on the actual kid side of things.
Retailers pushed for smaller assortments/smaller cases so they wouldn't be sitting on product...but then don't fill their own damn pegs.
I have observed at Walmart, especially, is more prone to carrying a "single item" than they used to be. They don't carry a "Spider-Man: BND Actionverse" figure assortment, they JUST stock Hulk and the base Spider-Man (meaning this store won't actively stock Scorpion or the black Spider-Man deco). Many have never carried a "Prime Changers" assortment, it's just been character specific. My store JUST carried Prime and Bumblebee for TFOne. This spring, they have two pegs for Optimus Prime, one for Bumblebee and one for Megatron. It remains to be seen if that will change for the holidays. The Star Wars section at my store has 4 pegs for ActionVerse figures, one for each of Mando, Grogu, Zeb, and a Stormtrooper. The 3 pegs for Black Series are all "general assortment".
There's positives and negatives to each approach:
Pushing for set character assortments, theoretically, should streamline the reorder process and prevent one poor seller from bogging down the entire segment. However, with retailers continuing to push back against any expansion to the toy department, if not outright cutting it (again, increasingly common at Walmart stores), it makes it difficult to ensure character exposure and inherently limits the number of characters a year. Even with a more modest cast, would that stop a Walmart from opting to JUST carry what they perceive to be the most popular characters?
Hasbro has released 4 ActionVerse figures for Spider-Man BND (not counting pack ins and exclusives), and 4 figures for "basic" Spider-Man. Those 8 are the extent of the ActionVerse selection will offer for the ENTIRE YEAR and you still have situations, like my Walmart, which won't carry the comic Spider-Man or Spider-Gwen to simply carry Miles, Venom, BND Spider-Man and BND Hulk across TWELVE PEGS.
The wave system allows for greater variety of characters, but are seemingly more dependent on product sales. A couple figures don't sell? That assortment might as well be "dead" until they clear it out to replenish. The Snake Eyes movie, particularly Baroness and Akiko, pretty much killed GI Joe Classified as a recurrent product line at many locations for YEARS.
