Two thoughts and personal observations on that:
1. Nobody was ever fired for buying IBM. In my impression it's usually deployed as default for and esp. by very tech affine communities. It was the new, hot - and is now save - thing in town.
2. You see postings boasting how the Discourse forum is now powered by a new six core 8 GB RAM server improving performance ... for 200 concurrent active users and 80k posts. Yes, Discourse offers a lot of flashy features, but that's just borderline disgusting.
I guess companies that use Discourse and have huge traffic can pay a bit more, nothing wrong with that.
The point being that said numbers aren't big traffic, they should be handled by a Raspi.
But for the sake of argument: Discourse is a painless move upwards for big budget and/or big knowledge entities. Nothing wrong with that.
On the other hand Discourse isn't a replacement for low cost, decentralized, easy to deploy, engine-diverse, low knowledge communities which were served by a multitude of PHP solutions in the past.
There's an economic argument for a growing divide between "communities as a service" ala Facebook and high hurdle deployments ala Discourse, but one doesn't have to be happy about this development.
Much like Wordpress and phpMyAdmin, these projects are basically victims of their own success.
I don't see how. The repository seems to be quite active and has plenty of current pull requests.
I don't doubt that Discourse requires more resources than most PHP forum packages do, but it doesn't need that much more.
1. Downloading the application archive and uncompressing it
2. Creating a MySQL database according to the documentation
3. Either editing a small config file to give the application the database credentials, or even just going to the application's index page and filling in the details on a first run experience
And... that's it. Rails has no comparable experience, unless -- like Discourse -- you put in a lot of work to get it there.
Laravel -- and Symfony -- work basically like other "modern" frameworks do, for both good and bad. Laravel has "Mix," built on webpack, for instance. So if you're looking for that in PHP, it's there, but that's kind of a tradeoff in the context of small sites deployed/managed by a single person -- a use case that I think modern webdevs sometimes lose sight of. If we go back to the example of forums, those are very often that "one person wants to host a forum for their community" kinds of things. (And I'd like to see more of us get back to self-hosted blogs -- which is part of what led me down the road of "can you write something in a not-PHP language that's still easy for someone who doesn't know anything about web development to deploy and run." The answer still seems to be "reply hazy; ask again later.")
I'm not convinced that Discourse is the right example here, though. Arguably the actual steps for installing Discourse aren't significantly more complicated than WordPress's install, because they've gone out of their way to make it as easy as possible. (It does suffer from "you must use Docker for this," which would likely intimidate non-techies who could otherwise suffer through a WP install, though.) Also, I don't think Discourse can remotely be described as an abject failure, given that virtually every forum I've seen go up in the last five or six years runs on it, and I can think of more than a few sites that migrated to it from legacy PHP forums in that time.