Here's a prediction from the early days of Sun and Moon. I don't remember if it was particularly common on these forums, but I saw it a fair bit on the GameFAQs board.
"Offensive Z-moves (especially STAB ones) won't be all that great. Status and coverage Z-moves are the future."
So many people thought that status Z-moves, particularly Splash, the omniboosts, and the full heals, would be the hottest shit. After all, why would you waste your Z-move on a single strong attack when you can have a slightly smaller power boost at all times with Band or Specs? The answer, as it turns out, is that Z-crystals don't effectively prevent you from boosting your stats through regular means. Almost no one seemed to realize that a Swords Dance boosted Z-move would blow Choice Band out of the water. And whenever offensive Z-moves were given the time of day, the focus was usually on coverage moves. I remember a comment of my own that postulated a Dragon Dance Dragonite using Z Iron Tail to smash a Fairy-type trying to stop its sweep (at least I recognized the synergy with stat boosting). While coverage Z-moves certainly proved to be effective, almost no one predicted that using a STAB Z-move to deliver a nuke strong enough to chunk resists and demolish neutral targets would be equally as effective.
Oh gosh this reminds me of how naive I once was
Before Sword and Shield came out, I had to admit - begrudgingly - that, despite everything I disliked about it in context
"it looks ugly and out of place," "we lost Mega Evolution for this?" and "honestly I really hate the move to super mechanics like this being a set of rules to affect everything at once - can we go back to them being entirely on a per-Pokémon basis like Mega Evolution instead?" being the main ones, Dynamax actually looked like a really interesting battle mechanic in its own right.
I liked that it was designed to create cool setup opportunities rather than being just raw attacking power like offensive Z-Moves, and I thought the temporary bulk increase was a good way to facilitate that kind of setup rather than directly increasing offensive power too much.
Especially when we learned that the stat changes also affected allies in doubles, I thought it would be on the tame side when used by a single Pokémon, with its strongest potential being in ally support/setting up two Pokémon at once and generally more in strong and creative combinations rather than just turning one Pokémon into a complete menace, and I thought it was cool that its main benefits seemed to be defensive and focused on giving time to set up and stack effects rather than on breaking power.
I think I personally was a bit too optimistic even for what we knew then, but I don't think
anyone expected it to be as broken as what we actually got. I think the general consensus at first was similar: "don't love the aesthetic, but it seems mechanically sound and more interesting than offensive Z-Moves" - I had seen plenty of other people voice the same assessment in the prerelease period.
And I certainly don't think anyone even
considered the possibility that the entire mechanic would end up banned from OU
and DOU
and doubles is where it's supposed to be the most balanced! and also have to be restricted in Ubers... right up until we were actually playing and understood how it worked.
Honestly, I fully expected Dynamax to be a fascinating and well balanced mechanic right up until it actually happened, haha.
Somewhat amusingly, my opinion seems to have done a full 180 - at this point, some of the Gigantamaxes' designs have grown on me enough that I
don't have such an issue with the aesthetic design of the mechanic any more,
only the gameplay itself, haha.