$70M is not a huge amount of money for an animated movie in 2015. As someone who is a life long huge fan of animation, I can promise you this. There are no other $70M 2D animation movies right now so there really isn't anything to compare it to, you'll just have to trust Don Bluth a guy who has worked on dozens of extremely high quality movies (and dozens of terrible ones too).
Comparing it to the 2011 Pooh movie is off base, IMO. That's as nice movie, but the (beautiful) backgrounds are mostly static. There usually aren't more than two characters on screen at once. The settings and stories were mostly completed nearly a century ago. It's also extremely mild. Mild saves money.
If this DL movies gets made (which, I'm not sure I even want it) and it's what it should be (let's hope) you'll have new characters animated on 1s with no digital in-betweens. You'll need to have a lot of new stuff, nobody is going to be happy to see the same 35 year old designs going at it still. The FX animation for fireballs and giant diamonds and freezing winds and lavafalls will eat up 1/3 of the movie. The interior design of the castle will not be a quick thing. You have to have complex action sequences (more than Poohs ass falling out of a tree, that's great, but not really action) and then of course there is the thing that always gets done with big budget animation in the west, pissing away millions on big name voice actors for parts you could do better with scabs.
Inside Out cost $170M and its mostly screaming with a lot of eyes and hair moving. Cars 3 will cost even more, and it will stink. $70M is chump change. To me, the biggest worry is if it's possible at all.
These days people think all you need is a Kickstarter to make thing exist, but Bluth's golden era (which was pretty f*cking golden) didn't exist in a vacuum. To be top of his game he needed the worlds entire ecosystem of 2D animation to be on top OF. Thats gone now. Almost every bit of it. He needed a good supply of guys that quit Disney to work for him, for one thing, the excess industrial personal runoff that will come from a company that employs the very best only to hugely limit their creativity and piss them off. Disney doesn't have 2D animators anymore, not many anyway. Most 2D animation in the world today is farmed out to Korea for the lowest possible cost and done with goddamned vector graphics. An episode of Family Guy, which is pretty much just crap, it's over $1M. The Simpsons is more than double that. To make cheap shit they've made a million times before. $70M ain't shit.