Also there are a lot of deprecated things that must have been removed in 3.1 ― TBH I haven't kept in touch with 3.1 development but I'm sure a lot more has happened besides the default switch and Asset Pipeline. :)
Basically in the end, Rails is a curated framework. It either fits your requirements or it doesn't. There is no need for it to work for "all possible" cases.
Also like I said you don't have to use the defaults. :)