Performance of Ruby is often terrible. At some point GitLab will have to recognize that. I know they have some Go in the stack, but so much is of the application is hinged on the Ruby monolith.
2. I didn't ignore the whole article, the article ignored my concern save for a few sentences.
Whether they have to act on it? Maybe not.
Almost all of Rails codebases that I worked on, had performance problems (in that it was hurting the bottom line). But most often, the solution was found elsewhere: tune the database, use AR smarter, spin up more servers, buy a bigger database server, etc.