Ok, here's my response...
I'll use whatever gets the job done. I don't care about the 'best' or 'latest' bells and whistles, unless a client wants and needs them. I've used Joomla, and found PHP and other 'CMS' systems and their modules not as intuitive as you suggest. The availability of free modules doesn't mean much in any framework unless they provide a solution for the client with whatever level they need.
With DotNetNuke the 'bulk' is very much there, and there is no lightweight version, and that's probably, a valid criticism if you don't need all of the 'bulky' features. However, that's the market being targeted. I don't need support for a lot of what's actually in DNN, but it hasn't stopped me either. As a developer, it seems to be more of a task to keep up with developing modules in DNN than some other 'frameworks', and that's why there seems to be a lag in development of open source modules. I guess, it comes down to preferences and taste. If you like something about the framework that works with your native O/S preferred environment, then, it's worth putting up with the issues associated with it. If your client wants to use something else, well, you help develop the solution, or lose the client.
I would say that the DNN community is fairly large as well, but in the past year or so, the actual number of folks that respond with 'real' help has dropped off. I don't thinks it's a statement of lack of interest, but because most folks with expertise are 'busy' doing work that helps pay the bills. I know I don't do much developement, but do try to engage in assisting where I can, and know lots of folks that do the same. The DNN community is pretty friendly, and helpful in my experience. The only thing most folks ask is that there is some kind of effort to 'read the existing' forums for a first pass at a possible solution, and basic searching of the 'ethernet' for help. There is documentation, and like a lot of other frameworks, it's the last thing to get updated. I've been on forums of other O/S based frameworks, and don't find any better or worse help. Documentation is not always as good as it could be for anything, but that's been the case in my experience of over 30 years of IT/IS work. I've worked on micros to high-end Mainframes, and like a lot of things, I've come to appreciate them for what they are, but don't rely on only using just one type.
Now, I can't say that DNN is always going to be the best framework for every case, but once you understand how it works, know your way aournd in .Net, have the tools, and knowledge to work with it, DNN provides a very scaleable and cost-effective framework.
In the end, it isn't the instrument but the musician that makes the music.