While I'm still undecided on where I stand with terastilization as a mechanic, I still think it's without a question that Dynamax was the worst mechanic ever conceived for Pokemon.
Megas had their share of issues for sure. Mainly popular Pokemon getting them, their lack of balance in many cases, and a handful of times, the Mega being worse than the non-Mega paradoxically, but as a whole, they were cool. You could only use 1, and you sacrificed your held item.
Z moves were, bad, but inoffensively bad. They were primarily a nuke button, though there were fringe cases where you could use it as a superbuff, but there was a legit tradeoff to it, in that it was one time only, and you lost your held item.
Dynamax, what can even be said that hasn't already. Doubling your health and doing secondary things like stat buffs for free or setting trapping/entry hazards all attached to Z-Move power moves, which lasted for 3 turns, and you still got your held item on top of that. Who thought this was a good idea again?
Terastilization, I'm not entirely sold on it being an okay mechanic to be blunt. With things like Megas, Team Preview pretty much pointed out with big, red arrows which was the Mega Pokemon, and Z moves were one and done. Tera is something that you basically can't prepare for, since said info isn't readily available.
Which is frustrating, since it's deceptively powerful since the power doesn't seem as front-loaded as the other mechanics, but being able to change a Pokemon's type into something that's advantageous to it on a single button press is frankly unheard of and unpredictable. I feel like if Tera types were readily available for both players to know, it'd be one thing, like they do in VGC, but as is, the mechanic's kinda sus, ngl.
