Ecto was literally the component I liked less in all the Phoenix stack when I worked with it after a dozen of years of Rails.
I did maybe 5 years of Phoenix for a customer of mine and went back to Rails for another customer. It's good enough and overall Rails is easier to deploy IMHO. Capistrano vs I don't remember what.
Yes, that must be the case because if my customers and I would care about compile time guarantees we would not be working with Ruby.
In that years long Phoenix project one of the developers on the team added dialyzer type annotations to the functions in the files he worked on. Everybody else did not bother. The project ended up with no type checking. The service run and the company did well.
Overall using Phoenix was a good experience. I never used Elixir in any other project and never for my own programs. I use several other languages for my own little scripts, mainly bash, Ruby, Python and Lua. I think that I really like dynamic typing.
Oh man, this must just be subjective because I find Ecto to be beautiful compared to the absolute trainwreck of Activerecord. Having compile time guarantees through Ecto is wonderful.