I have personally not seen anything like Flarum before and that's after using every single common forum software available to date. I started with vBulletin many years ago before switching to IPB/IP.Board. Having used it for years and years there was talk on an administrator and forum owners forum I frequent called The Admin Zone about XenForo. So I jumped ship and loved the software. I honestly cannot remember at all how I stumbled upon Flarum but I'm pretty sure I was referred to it from Toby's very first forum software called esoTalk. When I first installed my own instance of esoTalk I knew that Toby was heading in the right direction and I instantly became a fan of his work.
And now here I am.
Since finding out about Flarum I have basically taken down all previous forums, saving me hundreds of dollars after paying for the software and updates every month for a couple of years. So there's one major pro to use Flarum; it costs me nothing except for a cheap monthly hosting bill that you cannot avoid if you want to have an online presence.
In my honest opinion there are enough active members here on Flarum. There are numerous members that post daily, others that float around weekly and the usual person that basically reads up on topics and posts without replying. Just because you can't see activity doesn't mean it doesn't exist per say. That may seem a bit vague but it is true when you visualise it. When you mention higher quality code, well, Toby and Franz have the experience. I am a moderator over at Franz's own creation, FluxBB. I have been a fan of the software since day dot and still have two forum instances using this software. Why? It serves my purpose and I've never been a fan of migrating to other platforms (for some odd reason I would rather start fresh than migrate). This also means I have no plans to migrate to Flarum. I do have Flarum installed on my main project and that is where I make the connection. The feedback I get is extremely positive and apart from not having a private discussion/message feature out-of-the-box, there are no negative comments made to date. To make my point, I do believe that once we hit stable there will be plans to include additional staff if need be. Unofficially speaking, don't fix what ain't broke. The current staffing levels are meeting expectation and as Toby has mentioned already, the beta label will be dropping soon and we are steaming ahead to get us to the milestone everybody wants.
What you are doing @Sanguine is amazing for Flarum and its community, both present and future. I initially planned to create such a service myself as every one I saw making an attempt for something similar failed. I have always been interested in hosting services and have created two or three myself. One was successful but the others didn't go according to plan. Trial and error, and when you are taking on something new there is always going to be new things that you won't understand until you think it's too late but if you stick it out you will soon learn that projects go up and down in peaks and troughs. So long as you maintain your momentum, stay motivated and dedicated, you will always come out on the other side with success.
I believe that power users have been catered for already short-term in the form of Patreon. When you make an investment in something you will always be more interested in how it progresses. Look at it as buying on the stock market. Not one person makes an investment to lose money, but if they see progress in their investment however big or small it may be they will keep their interest and potentially buy more. I believe there are more ways Flarum can cater to a "power user" but it doesn't have to be the sole focus, it can be a joint focus for the developers. You don't want to cater to one type of user and leave the rest in the dark, but I too believe you can't please everyone and that's just the way the cookie crumbles. It is a bigger job trying to please everyone but it isn't an impossible feat.
2018 is going to be a very big year for everyone here at Flarum. A little more patience is required but it is going to be worth it guys. Toby, Franz and the rest of the team are currently working their butts off to give you the product you want so much. The day will come and it is creeping up closer and closer. Flarum is and always will be a direct competitor to any forum software on the market but the best thing is that the software speaks for itself.
And that's a longer post than I initially thought. ? I may have missed a few things out but will revisit them when highlighted. Feel free to critique and comment.