>>52932985It has everything to do with the dex cut because Tera typings aren't coming back. There's no way they're going to devote any time or effort into integrating it into any future titles when that time and budget would be better spent propping up whatever new generational gimmick they're developing, especially when they've shown that they'll get rid of far more straightforward or important concepts for less. So mons that relied on Terastalyzing to be good in SV are going to be rendered impotent in gen10.
Terastalyzing represents the jumping-off point for importing old mons where any further advancements along the timeline just isn't worth it anymore.
If you have a really great Hydreigon that you've been moving from game to game since B&W, its performance is only going to get worse after losing the ability to change its typing. It will continue to lose access to useful coverage moves, it will steadily decline in performance as power creep sets in, and whether or not it can be redeemed by some future feature is a complete gamble. You can either leave your mons behind in a game where they're good or hell, even exist, and they can continue to be good and to exist for as long as you have that game; or you can keep dragging them through the mud while reminiscing about how good they used to be.
