First of all the animation has never been quite as awful as you're making it sound, we've already had a few specially animated episodes a while back during the Kuma teleportation ep and Luffy vs Snake sisters

And that's not how it works, we don't get specially animated scenes, we get specially animated episodes. A few somewhat important scenes don't warrant that level of animation, and you know it as well as i do that there are episodes to come that warrant it a hell of a lot more than these do.