Sadly, as Rick pointed it out, Xojo’s size (which we all do our best to increase) hasn’t reached the critical mass for some of the things vastly popular languages take for granted.
People compare Xojo with VB, ObjC, PHP or Python. While this is really flattering and appropriate, quality-wise, different factors have made Xojo lag behind those in terms of size (I won’t delve into the reasons for this, since the ones I can think of are too simple and possibly oversimplified).
But with size other things come. People doing their own forums, communities, repositories is one example. Add-on managers, proper common plug-in directories frequently maintained and updated, etc.
Xojo has had this in the past, but it’s always been the work of extremely dedicated individuals, doing the work that in other platforms is shared among many. As with any project lead by one, the probability of it being excellent or of being maintained frequently swings wildly.
Xojo keeps growing, and things will eventually come to pass if it continues this way. For ObjectiveC it took 20 years 
It’s also true that Xojo as a language and development platform attracts both sides of the spectrum. This results of this obvious conflict of priorities between hobbyist developers, extra-income developers and professional developers (even here, some develop for the free market and others specialize in custom solutions built for their own customers).
By Xojo going free for the IDE it was to be expected (and welcomed) that the community would be interesected by developers of free software used to free software resources testing the waters.
All these types of users must learn to live together, since any other way can only be detrimental. It’s frustrating to see people from either side deciding they have the One True Word of how the Xojo forums or Xojo development must be made. It’s also a serious turn-off for newcomers.
I, like Rick, wish for such a resource to appear. I also don’t have the time to do it myself so I’m content with seeing Xojo grow and wait for it to appear eventually (or for current initiatives to grow and cover this need).