Ruby is extremely consistent in that everything in it is a class and it's thoroughly OO. I'll admit it's added some new things in the past decade, but nothing close to to the decades of accumulated cruft JS has.

The really amazing part of JS cruft is how constructs that should have been dead for 20 years just keep coming back. E.g., the keyword "with" is a footgun for hiding object scopes that mostly disappeared before I learned JS, but then it showed up in Vue of all places!

Variables are scoped either to blocks or their enclosing functions, depending on how they're declared. Functions either create a context for the keyword "this" or not, depending on how they're declared. Both of these traits are maddening for learner.

JS uses a prototype chain and prototypical inheritance, but now also has a classical-looking class-based syntax as well. There are half a dozen ways to create an object and it's a much bigger hurdle for people to learn than Ruby's more or less mainstream choices.

Building larger apps in JS on the back-end also means spending a lot more time thinking in callbacks, promises or async than working with Rails would, too. Sometimes it's inevitable but it's a hurdle for learners.