It's biggest issue in my opinion is that addons can't keep up with the release cycles even being them slow ones. That makes you not to rely much on them becaus

It's biggest issue in my opinion is that addons can't keep up with the release cycles even being them slow ones. That makes you not to rely much on them because in the long term you couldn't be able to upgrade EmberJS due to your outdated dependencies. Of course you'll be politely reminded that you can PR an update of those addons but there are some casuistry like the owner not being reachable or not willing to accept your changes. Apart from that, it's delightful to work with it.