It is meant to deter questions such as:
"What is the best genealogy database?"
"What is the best website for publishing my family history?"
"I need a list of open-source genealogy programmes."
i.e. questions without any supporting criteria that could turn into a popularity poll for a long list of options, without any criteria specified for what 'best' means to the OP (so there can't be one or a few good quality answers, just an opinion about loads of things that might or might not meet the unspecified need). The relevance of the answers will probably vary widely with time, and list answers don't help other users.
It isn't meant to deter questions such as:
"What possibilities exist to achieve X goal. It must be simple to use for somebody who isn't a computer whizz-kid, and work on Windows 10. Cost isn't really an issue".
"Is there a utility that will do Y? I use ABC as my main programme, so would want something that will work with that data format or with a Gedcom export."
"What factors should I consider when looking for a genealogy database programme to replace XYZ. P and Q are essentials for me, but is there anything else I should take into account when making my choice?"
i.e. questions with a specific problem to solve and specific constraints and/or criteria for a good solution -- the set of answers will likely be limited and should include explanations about how the solution proposed will meet the need specified, not one line answers. The answers may become less relevant with age (true of many questions on many SE sites) but good answers will include enough information about good approaches to the specific problem that they'll be relevant to others as well as the OP. (In the same way that a good answer to a question seeking a 'fact' about a specific ancestor includes how to approach the problem, not just what the fact sought is.)
I'd compare it with questions on Drupal Answers -- very often there's a question about how to do something specific in a specific environment, and the answer is advice to use a specific 'module' and how it will solve the problem; however it's in the nature of Drupal that there are multiple competing modules that perform overlapping tasks, so a question may receive multiple answers proposing alternatives (or there may be only one good way of achieving the required end result, but the OP can't know whether there's one or many answers when they ask).
They've dealt with a very similar issue:
Is it ok to ask what type of modules can help you accomplish a feature
Their on-topic/off-topic spiel includes:
and it is not about…
Comparison between Drupal and other CMS's, blog software, or similar software
which makes me think we could better reword
Which genealogy software or website is “the best”
Comparison between, or lists of, different genealogy databases, utilities, hosting services, etc.
and make the on-topic list more explict about
asking for software solutions to solve specific problems
perhaps with some guidance added about how to frame a good software question.