Plugins become orphaned and support via WordPress forums is not available.
Stack Exchange system is not a forum and not meant to provide general support.
Because a category of questions may require "detailed knowledge" is not a reason to restrict them out of hand. Plenty of questions on SO require detail knowledge.
The issue isn't as much how "detailed" knowledge has to be, but how wide scope is.
At the moment we limit our scope to: WordPress core, core themes, featured plugins, few closely related projects. That's scope size of a couple dozen items.
Total count of all items in WP ecosystem? Tens of thousands.
Practice showed it is simply not practical to post a question about something random out of such a wide scope. Probability of an expert with such specific expertise seeing and answering becomes a lottery with unwinnable odds.
StackExchange is generally a better support site.
Stack Exchange is not a support site.
As per tour the purpose of our specific stack, as subset of SE network is (emphasis mine):
With your help, we're working together to build a library of detailed answers to every question about theme and plugin development, development and management best practices and server configuration for WordPress.
This might look similar to support at times, but goals of the system are simply not meant to be support.