Of course Hugo has grown and it is complex, as it has been in active development since 2014.
As someone who is not developing Hugo but who has spent a considerable amount of time contributing to the Hugo Forum as well as being a former maintainer of the Hugo Themes Showcase, I know first hand that when things break down, we do issue detailed instructions about fixing the problem.
Also please note that things do not break that often. Typically there is an advance deprecation warning, but sometimes things break upstream or due to human error.
Usually one can find a solution to a problem through this forum and the Requesting Help guidelines do contain useful info for anyone seeking help.
As for the Documentation of course one needs to invest time.
On a side note, currently I am learning French and it feels like I am in elementary school again.
I couldn’t possibly expect myself to read Victor Hugo’s Les Misérables in the original without spending the prerequisite time.