I think the author is trying to compare what it takes to create an MVP web-app with all modern features versus creating it in the JS ecosystem.
Also, Rails is well known to have Convention over Configuration. That helps to set up and maintain a project since everybody has to follow the same pattern. The cons is that you lose flexibility from the architecture perspective. But in Rails, you have ways to overcome that easily.
I think Rails lost popularity when the front-end JS framework movement started. Rails didn't have a response to that; people had to create the Rails app, remove the Views and use a JS framework to create the one-page app experience.
Now, if you are already spending that much time using JS for the front-end, why not use JS for the backend? But then things got too complex in the JS due to the lack of conventions.
Also, Rails is well known to have Convention over Configuration. That helps to set up and maintain a project since everybody has to follow the same pattern. The cons is that you lose flexibility from the architecture perspective. But in Rails, you have ways to overcome that easily.
I think Rails lost popularity when the front-end JS framework movement started. Rails didn't have a response to that; people had to create the Rails app, remove the Views and use a JS framework to create the one-page app experience.
Now, if you are already spending that much time using JS for the front-end, why not use JS for the backend? But then things got too complex in the JS due to the lack of conventions.