I don't know if thats true. I've been working on Rails apps for over 10 years (some poorly written.) I worked on one particular Rails app for 7 years.

I've also worked on Java, Go, Elixir, and Haskell codebases.

I find that anytime we went "Slow" was because of decisions that were made around the data model, which can happen in any framework or language.

The thing that I love about working in Ruby is Rubyists tend to write fantastic tests (which double as documentation of what ever business logic), and the culture around "convention over configuration."

So even when we decided to port one of those Rails apps to Elixir/Phoenix, it wasn't an absolutely awful rewrite.

Is that true in languages like Lisp or Smalltalk? Is it true with Rails?

Future maintainers will go slow no matter what.

That isn’t my experience. Using a good statically typed language means that refactors will be fast. Using Ruby/Rails or similar means that you may not be confident after you’ve introduced important changes in your code base. So you might be more conservative? Take more time, do more testing (than was necessary if you used less meta programming and a more statically typed language)