C++ is not a superset of Object Pascal, rather, each have their niche features. I probably felt the same as you when I first upgraded to C++, but that followed by some disappointment, too. I missed sets as first-class data, the subrange type and many other big and small things. And the object model was quite different. I'd even argue that if you forget about operator overloads in C++, the rest looks quite weak when compared with Object Pascal's OO model. The article mentions some, e.g. virtual constructors, properties, etc.
The rest is basically in the article. Lots of features that are still missing in the mainstream languages.
And most importantly, the final binaries you get with Delphi are indistinguishable (size, speed) from those produced by C/C++ compilers, if not better sometimes.
If I were OP maintainer, I'd probably bring the language to today's "standards" if that's the word, by adding just a couple of things - anonymous functions, probably yield semantics, also foreach and better support for built-in dynamic arrays.