No, not really. The AI is pretty easy to defeat in >99% of the battles. With some basic knowledge of type effectiveness and higher in-game Pokemon levels, you can sweep through the game like a breeze. The only exception is, as usual, the Battle Tree, which requires more Battle Ready Pokemon to take on the more challenging battles. The first 20 battles aren't generally so hard, but the difference begins to show and soon the AI can easily overwhelm your untrained team.
So, if you're not looking to spend a lot of time in the Battle Tree, you need not waste time and effort in search for the perfect team. If you want, you can look for a right nature, and try EV training too, but IVs are really out of question. You always have Hyper Training for that.
Another point to consider is whether or not you want to participate in the Live events, like VGC and so on, then you'll definitely want a perfect team. However, this can be done post game and need not interfere with a casual run through of the game first