So... I've been programming in R for over 20 years. I've been ready for an alternative for performance reasons for about half that time. Julia seems like a promising alternative, that I wish I could use all the time instead of R but it's just not there; I'd prefer Nim most of all but that's even less well-resourced in terms of libraries. Maybe a zero-cost abstracted offshoot of Rust will eventually come to have a role? Who knows.

R, like Python, has far outgrown its initial scope. I don't think it was initially envisioned to be used the way it is today. But both have been kept in use as costumes for C/C++.

One of the things I've noticed the most in the last 20 years, to your point, is that the language used to be a lot more straightforward and simpler, more predictable. Over the years a lot has been added in a sort of haphazard way, and as a result today you have this kind of Frankenstein language that isn't what it started with.

As for data structures, though, I don't really see R as being that different from other languages. Many of them are the same as in other languages, but just have different names (and I do wish they used similar terminology). Others have been taken up in other languages as people have come to appreciate their utility.

Being a wrapper for C/C++ can only go so far. Eventually you have to write in R (or Python) and the speed shows, if you have enough data to deal with.