What version of TP? The linked articles is about TP3, which lacks common prog lang features that later versions definitely had (like proper modules or objects).

If you take a look at later versions or even early Delphi, I'd say garbage collection. Other languages from the Wirthian family had it, like Modula-2/3 or Oberon.

Lambdas/first class functions.

Unicode support.

Syntactic sugar up the wazoo.

Other than that, I think one could be very productive in a TP 5.5-ish language even today. The rest would be mostly about the infrastructure and community, like IDEs, package management and Medium posts with lots of memes.