Ruby has implicit imports which pollute namespaces. This is extremely annoying for anyone who wants to learn the language.
It uses extensive monkey patching, which is once again a substantial challenge for a beginner that wants to understand what their code is doing.
It has a nicer syntax with procs and lambdas but syntactically distinguishes between them with different ways of invoking functions and all the issues associated with bindings. In Python all functions look and behave the same, to the point where methods have an explicit self argument to make it clear that they're just regular functions (the semantics for function binding could be easier but then again such is the case in all object oriented languages).
Python's challenges are superficial syntax; the semantics are extremely uniform everywhere and don't suffer from special cases galore.
I don't think either of those issues, namespaces and monkey patching, are things that make the language harder to learn. You require a file, the file's namespaces are available. How often do libraries modify your runtime with monkey patches in a way that you'd notice? I'm sure it's come up during my career, but not when I was a beginner. There was a period of time when metaprogramming was more popular in the ruby and rails community but that was some time ago. Still, it's a tool that's nice to have available.
I vividly remember how I was told that you could write "2.years" in RoR.
So, if you copy that code snippet and run it as an independent script, it would just not work because it was a RoR monkey patch method.
Worse, the implicit imports mean that unless you have a global view of which files and gems are require-d, you don't know what your code is actually going to do.
That, and coworkers suddenly feeling at liberty to override `method_missing`, abusing `bindings`, and all that stuff, makes it really hard to like the language if only for its tendency to bring out the worst in people.
Requiring a file from a library that's part of a framework's source code can be quite challenging as it requires either the complete docs or perusing the source code to fully grok what's getting included, especially with the monkey patches.
I don't know the current state of the RoR ecosystem but back then when both languages were competing for similar mindshare this was a massive turnoff.
Python's challenges are superficial syntax; the semantics are extremely uniform everywhere and don't suffer from special cases galore.