I'm not a big fan of surveys and I'm not sure I've responded to this one actually, but: my current feeling around Phoenix is that it will be my go-to framework for anything web related for the years to come, but also Elixir will be, for larger topics (ML, embedded, data-viz, scripting, etc).
There are a number of important points (to my taste) that comes out of my use of Elixir & Phoenix :
- the maintenance story has been quite good (maintenance work is one of my main line of work since year 2k, I have used many stacks, including Java, .Net, RubyOnRails etc). Upgrades and refactoring & moving code around has been quite easy overall, once you get the stuff right (using Mox etc).
- Phoenix, Ecto & Elixir are a good "generalist web framework" for a lot of use
- Compared to some stacks (non-evented Ruby & Python, for instance), having a part of your app work as a proxy for domain-specific uses, is not a problem, and does not even require you to split that part from the main app (example at https://github.com/etalab/transport-site/tree/master/apps/un..., where we proxy/cache GTFS-RT protobuf & SIRI XML feeds behind rules, adding rate-limiting & hiding target server authentication schemes)
- Similarly, anything real-time is at least initially trivial. For instance, creating this real-time view of moving vehicles (https://transport.data.gouv.fr/explore) with 70+ GTFS-RT feeds has been quite easy (PR at https://github.com/etalab/transport-site/pull/2224). The server side is like "EventMachine done right", and the live updates are broadcasted to each client via web socket. No extra server (e.g. AnyCable) or anything is needed.
From a perf/ops POV, the amount of topics you do not even have to think about is quite important, which is very nice.
Overall I can see myself sticking to this stack for the next 15 years or so, without much worries (I've been coding since 1984 as a kid, so I have a good idea to know when to keep a framework around or not :P)