While I find Riccitelo’s comments about “competing with their costumers” crass, the fact is that Unity and Unreal Engine do have different business models and, more importantly, a different “core costumer” (even if they overlap in some areas). Epic, IMO, is simply not yet used to managing a large novice developer userbase. The userbase Epic is familiar with compiles from source, uses Perforce, and asks questions detailing the engine source they already modified trying to fix their problem.
This userbase also gets their own VIP lounge: UDN, which is the first-class version of AH, where Epic staff will post an answer to pretty much every question (even if it’s to close it for tracking purposes). Back when the community was small Epic staff was able to tend to UDN and spare some time to AH and the forums but that looks no longer the case. To make things works, the noise-to-signal ratio grew with the community, harming its ability to support itself.
This brings me to the point I consider most critical in AH: noise and clutter. Someone already mentioned StackOverflow, and the reason it works so well is the quality of the questions is fiercely moderated. Meanwhile in AH too many questions would need a “what have you tried” to move anywhere, plus the duplicates. All this noise buries the good questions, discourages people who are capable and willing to give support, and lowers even more the possibility of having Epic staff replying. The AH really could use a cleaning and a moderation staff to keep it clean. The staff doesn’t even need to be knowledgeable in Unreal.
The forum has similar problems but in a somewhat lesser scale since bad questions will usually move away from the first page as nobody is able to answer them (unless the poster angrily bumps their own post). Still, having a stricter forum moderation would help: locking those half-decade thread necros (or auto locking threads after a long inactive period), merging threads, deleting double and cross posting, enforcing threads to be on-topic, and maybe even locking simple question threads that would be better off as AH questions.
BTW, over in Unity land there’s also problems with information being split between their answers website and forums. Maybe it should be considered if having both things isn’t itself a problem.