I was always a bit hazy on what these terms actually meant, and what we lost. It does seem like there was a brief golden age of easy "rapid application development" tools like FoxPro where you could wire some UI fields to a database without too much trouble. Now we have people trying to do the same in the web, badly.
I also had no idea what client/server meant (at the time). My current oversimplified distinction:
Workgroup: I/O thru file system, clients responsible for locking, concurrency, etc.
Client/Server: I/O thru DB's protocol (eg TDS), server responsible for locking, concurrency, etc.
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As for what was lost, I spent way too long (10+ years) trying to figure that out, trying to fulfill the desire to recover the ADO (Access Data Objects) programming paradigm. I think I succeeded, more or less, and am currently reorienting my life to work on it full-time.
I used to loathe FoxPro, now I actually miss it, it was simple enough to quickly get the job done. I have always thought in the 2000s that something better, more powerful and even easier to use would come. And looking back I felt a lot of times technologies general we reinvent the wheel and nothing better actually came out of it.
FileMaker may be an alternative, but I never understood why it hasn't caught on.
And I am not even sure if there are any product similar that is good on the Web.