Two primary reasons:

1. Ruby is a very flexible language, and that has its ups and downs. While it makes it a very pleasurable easily modifiable syntax, it also leaves a lot of room for bad patterns. Ruby won't judge someone for taking an ill-advised approach to a problem, so it's easy for newcomers or novices to lay foundations that cause trouble later on.

2. Ruby is very prominent in startups, which are the companies most interested in immediate results. This often leads to favoring short-term advantages such as getting a feature out today to secure a deal rather than long-term advantages such as taking the time to keep a maintainable code base. Some startups with strict budgets will also hire people with less experience early on, leading this to pair with point 1 more often than we'd like.

That said, I'm a Ruby dev and have no interest in working in any other language (other than JS on the frontend). It's a beautiful tool to those who treat it well and I'll happily use it for just about any project.

in my experience, the main pain point people experience is:

a) they don't like Ruby for whatever reason, b) they probably only deal in backend or only deal in frontend, and so don't understand the value of the bundled dev experience rails delivers, and therefore c) because of a + b they find the moderate learning curve to be extra painful, so they lash out.

at the end of the day it's all just code. why would it be harder to integrate a service in Rails than in Go? of course it isn't.