I think the whole "thin is better" concept with devices these days is really messed up. Instead of putting a big battery in devices, they build them almost razor thin and use small batteries. If you carefully read the advertisements for the battery life of the Oasis 3 and then do some simple math, what sounds like weeks between charges is actually marketing-speak, and it really translates to 21 hours of estimated use with BT and WiFi both off and the screen light set fairly low. So yes, if a person only reads half an hour a day and never turns on WiFi or BT and keeps the light off or at least below level 14, then they might get a few weeks before having to charge. But why pay $250 for a reader if you only rarely use it? Most people that buy them likely read a lot more than that, and many probably have at least WiFi on. If they use the Audible feature, then they have to run BT as well. In my case, I leave BT always off, only use WiFi for a few minutes each day to use Whispersync so my place in my books is available across all my devices, and I rarely get more than a few days between charging. But I read several hours each day, plus I charge before it falls below 30% which is better for the battery in the long term. I would be willing to bet that if we could completely disable about 90% of the Amazon BS marketing features we never use, all that stuff designed to sell us more books, the darn battery would likely last a lot longer. But Amazon isn’t going to give us that option before the 12th of Never.
Sorry to hear you couldn't get your Oasis 3 to work out for you. I finally seem to have one that is good and I’m very happy with it. I’m not happy about the Amazon Cloud not working correctly with either of my Kindles though, but that is almost certainly due to terrible Cloud programming rather than an issue with the Kindles. I cannot see or adequately manage universal collections using the Cloud when it comes to the Kindles, so that means extra work creating and managing the collections directly on each Kindle, which kind of defeats the purpose of even having a cloud IMO, but at least I finally have my Oasis 3 set up the way I want it even though it took way longer than using a Kindle app on a non-Kindle device. That wasn't a deal killer by any means, but it is certainly aggravating.