I'm a Python developer now, but I still miss the ease of writing code in Ruby. I find it a cushy, intuitive activity, and I wish it was used for something other than hulking, poorly scaled/planned out web apps of yesterdecade.
When I first visited HN (~2010) it seemed Ruby and Rails was all the hype; doing Ruby/Rails stuff seemed to be the hip and cool thing to do. Perhaps Heroku was also introduced around this time?
Nowadays it seems Rails is mostly forgotten and Ruby, well ... Python seemed to have dethroned Ruby as Python seems to be used for similar purposes.
I tried to get into Rails in the past, but it didn't quite click with me. Perhaps in part because I don't do web dev by trade. In general I just don't enjoy web dev. Ruby as a language, I did enjoy and I used it in combination with Calabash for iOS tests. But I believe most of my team members didn't get the same kind of enjoyment out of Ruby as I did, much preferring much to work with statically typed languages, as such most didn't get involved in writing UI tests too much and just focused solely on the mobile app work.
I also used Ruby as a replacement for some shell scripts, when a shell script would be too complicated and problematic to write.
Just last year (after a few borked initial attempts) I really got into Lua [0] and I have to say, I enjoy it even more than I did Ruby in the past and also most statically typed languages that I've worked with (C#, Swift, Objective-C, ...). Lua (with LÖVE [1]) is awesome to me.
Lua seems to be a very neat small little language that is build on just a few very simple concepts, which makes it pretty easy to wrap your head around it. With Ruby there would be quite a bit of magic (complicated internals) happening, which I don't see in Lua.
Some people mentioned Lua might be hard to use in big projects, but I believe it should be manageable and I hope to write a pretty big game using Lua and LÖVE in the future.
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[0]: http://www.lua.org
[1]: https://love2d.org
Ruby's popularity peaked during Web 2.0 when almost all new apps were server-side web apps. When smartphones came out and a massive fraction of development shifted over to client side apps, it sucked much of the air out of the room for Ruby and Rails.
(And dynamic typing in general. Runtime performance is a fungible cost for server-side programming where you can throw hardware at it, but a hard requirement for client-side apps running on devices you don't control.)
That's basically it, for me, yeah. Long-lived (or hell, pretty much any of them that aren't just getting started) Rails codebases, even when they're not particularly complex, without heroic levels of good processes & individual discipline to keep things reasonable and clear, become fucking nightmares to onboard to. I'm more wary of Rails than a bespoke PHP codebase, at this point, and "we're a Rails shop" is damn near an instant "well thanks for the interest, but no" from me. I don't need that stress for the dozenth time. Just done with it.
It sure is impressive how fast one developer can knock together a prototype with Rails. Meanwhile I've had so many extremely-bad experiences with ongoing Rails projects that I hope never to touch one again.
But I actually like using Ruby itself a lot better than, say, Python. Ruby's fine. Rails... no. Never again. Maybe if they embrace static typing and it becomes nigh-universal in the Rails library ecosystem, they can make it tolerable. Too much magic, too little help from my tools to help me understand WTF the magic is doing, where it comes from, et c.
Gem's certainly aren't perfect, but I'd take them over Python packages any day.