I have a vested interest in this issue, since I recently asked about https://serverfault.com/questions/576648/solutions-for-integrated-management-of-l2tp-ipsec-vpn-clients-and-802-1x-wired and it was put on hold because it was perceived as a request for product recommendations. I know that product selection was part of the question, but it was part of the wider issue of building a solution for strong VPN & wifi authentication and certificate administration.
The issue that's repeated in response to questions about product recommendations seems to be that they become outdated. What I fail to understand is why this matters. Many questions become outdated very quickly as well, but it seems that because they're related to operations rather than to design and implementation, they're OK. For example, Resolving "php54w-common-5.4.24-1.w6.x86_64 conflicts php-common < 5.4.0" is a question I was able to help with; it will be not only out of date by the time PHP5.5 or CentOS 7 rolls around, but it's probably localised to a very small number of systems worldwide. Questions and answers have dates on them, and ServerFault readers can easily discern whether they are still relevant or not.
The answers to Where is an appropriate place to ask for server-oriented product recommendations? suggest that there is no place on SE to ask specifically for product recommendations, and if that's the policy then I guess that's your choice, but to rule out questions on solution design because they aren't 1. problem 2. solution style seems to fly in the face of ServerFault's aim to get professional sysadmins to share knowledge.
Maybe this is something that will never belong on on ServerFault, but surely there is (or should be) a place for people who build things to share questions and answers about why and how to build them. Does ServerFault not consider infrastructure design and implementation part of sysadmin?
EDIT: The cynic in me might point out Backup strategy for developer-focused Apple environments? (which is a strikingly similar type of question - if somewhat smaller) and wonder whether SF isn't a bit of an old boys club.