"But the truth is that the fireball isn't that exciting unless you care about the person running from it." - This is the key and you missed it by billion of light years. It is not about the character development it is about nobody running from anything. There is no fireball. Characters could be the best ever, they could even be so perfect you demand the government to let you marry them and it would make no difference. The "Inquisition Fireball" is static. It does not move. You just look at it and know it will never fall and will never hit anyone. As much as you care for the characters you know that nothing is going to happen to them. There is no threat. No fireball. Well, there is, the flash, the graphics. Inquisition is the graphic fireball without the threat of the fireball. We see a breach but there is no risk about the breach. Later we have Corypheus but Corypheus isn't going to do anything.
This is why you missed the point. The problem is not the characters. Is a fireball without impact. How will you care about a character, as much as you love them when you know nothing is going to happen to them? Dragon Age Inquisition in fact did not fail to deliver character for which we care, but nothing is ever going to happen, so what? When I do not romance Solas he is pretty boring. Same with Cassandra. Blackwall and so on... Because romance is the only "real fireball" in this game, the rest is just the looks, the light of a thousand suns but it hits you like a summer breeze. And well, even in romance what we have is mostly hurt, let's say the fireball makes a small burn far from the explosion it should be.
Corypheus is all "graphical fireball" with his godhood talk and threatening to conquer the world. But when the "actual fireball" hits, you barely notice, you laugh. So this is the problem, can you understand it? There is no fireball. No matter how much you care for Cassandra or Solas you know nothing is going to happen to them, nothing threatening. THERE IS NO FIREBALL. No matter how much Bioware invested in making it looking like the world was about to end, you can't absolutely feel any threat.
Making you care about a character is more than developing the character is about making something threatening to that character. Inquisition fails completely. personal quests are almost there, almost like the romances, but even with the (good) drama it never actually becomes a threat. DA2 had family dying. DAO too, even companions. DAI there is just no threat. (Bonus: Also, I miss having difficult choices in which your own companions would try to kill you or where you could be the threat to them.)