Delphi was and is not a low-code solution. It is a RAD environment where some really simple apps (i.e. the Fish app) could be built by dropping a few components on a form and linking the properties and writing a couple of events. But, most applications (and visual/non-visual component creation required coding skills.
What killed Delphi was stupid decisions by Borland/Inprise to move away from what they did best and become an "Enterprise" company instead of a developer company. They also concentrated on Windows-only development when other platforms (mobile, web, Linux, Mac) were becoming popular (see first f'up). And, they raised the price so far that even dedicated developers and can't afford it's stratospheric pricing ($2600+) - only Gods and birds can reach it.
The language is a dialect of Object Pascal (not in vogue despite its power). Delphi is the IDE and hasn't changed much over the years. It can now target Windows, Mac, iOS, and Android. Linux server is coming. It is very easy to create a highly complex, cross- platform application in a way that Xamarin can't touch. Performance for business apps is good. But, I have yet to see a real game written using it. And, good luck in getting Delphi into your IT shop these days (at least in the US).
Not until developers can afford it again and work with it to see its power (if they can tolerate the language), it will regain its market share.