To be fair, most of the issues are because of hardware incompatibilities, poor documentation, or lack of understanding on the users part. I'm not saying Unraid is trouble free, but with the vast array of differing hardware, it's hard to cover all the different contingencies, and the documentation consistently has lagged behind the product.
There are some hardware combinations that just don't work, but it's impossible to figure that out beforehand, so we just have to offer the best guidance we currently have, and hope to fix as many issues as possible, but there are some things just not under Unraid's control. Marvell and realtek's consistent disregard for the linux community in favor of microsoft is one example, there are many others.
For the most trouble free experience, find someone who is successfully doing what you want to accomplish, and copy their build. Unfortunately because of the fast moving nature of the PC business, it's difficult to post recommended parts lists, as that info is out of date within weeks or sooner sometimes.