Personally, I'm glad they removed attribute customisation on level up (though I would like to see it still there in character creation), not beacuse of "balance" or "simplifiying", but because having significant attribute increases on level up simply doesn't make much sense (and if the icnreases aren't significant, then there's little reason to include them).
At the beginning of the game, you're not some overweight couch potato for whom a good bit of exercise would seriously improve his physical abilities, you're already a trained <insert class here>. Your attributes will be, if not at your absolute peak, pretty good already. And as such, increasing them significantly over the course of the game doesn't make much sense. You will likely become a bit stronger, a bit more resilient and so on, but not to the extent that attribute increases on level up, at least how previous games have done them, would imply. I mean, in DA:O, my warden increase his strength fivefold over the course of the Blight. Even if you say that its not a linear scale or that zero isn't the start point, he still became significantly stronger over the course of the game. Which is not really plausible.
In order to gain major increases to your attributes, you'd need magic. Which DA:I's system of having your enchanted equipment as the main source of attribute customisation covers perfectly.
For the smaller increases in attributes that are plausible, well, I'd say that again DA:I's system of tying them to abiltiies makes more sense than having free reign to distribute them as you will. It's all well and good saying that "over the time period represented by my last level up, my warrior was focusing his training on agility", but then you go and take mighty blow as your skill, a skill clearly based around strength, it doesn't make much sense. On the other hand, saying you've been training to make "mighty blows" and as a result, you're strength has increase a small amount is far more logical.