It seems that they add items that could be great, but isn't always. I doubt they would want the rage from adding items that would significantly increase certain builds so much that everyone wish they had that specific item. I think it would be kind of good, to add a few super items to seasons. There will be people angry about it, but they just really need to do more with seasons because right now it's just dreadful. I don't even play season because I have zero motivation as it stands today.
Yeah but that's kind of my point, Crusaders already have an item that makes a build only possible in seasons and it has proven stronger than every other build available to class save the Stampede build (based on GR ranks). I'm not really seeing the outrage there.
Frankly I don't think Blizzard cares either way, I think the item situation with the first season is a result of them simply just trying to get each class with at least 1 competitive build, given that there was a blue post that said that quite literally. Try to get 1 good build in 2.1 and then try to add diversity as time goes on. It kind of just naturally makes sense for a lot of those to come from seasons anyway because it serves as a testing ground to see if an item is OP in an unforeseen way (resetting the GR leaderboard inside a season is not really a big deal compared to non-season) and like I mentioned before so far they haven't really added new items to the game outside of new content patches and we won't be seeing another one for a while. I doubt there will be another one until sometime next year unless somehow Blizzard magically stops being the same company they've been for the past decade, which, maybe can happen but I'm kind of jaded at this point when it comes to Blizzard actually releasing new content in a timely manner.