
In The Unified Modeling Language User Guide, the original developers of the UML - Grady Booch, James Rumbaugh, and Ivar Jacobson - provide a tutorial to the core aspects of the language in a two-color format designed to facilitate learning. Starting with a conceptual model of the UML, the book progressively applies the UML to a series of increasingly complex modeling problems across a variety of application domains. This example-driven approach helps readers quickly understand and apply the UML. For more advanced developers, the book includes a learning track focused on applying the UML to advanced modeling problems.
So we went back to whiteboarding and mostly doing top-down design (using decomposition to get down to actual data flow), and we got our products out the door.
In the meantime those books took up space on my shelf and ended up being more for impressing people who walked into my cubicle (remember cubicles?).
Now in my home office two of the three are makeshift monitor stands. I'm finally going to try to dispose of them somehow without harming the environment. I think they're recyclable.
I must say, the drawing (CASE) tools have always been missing even very basic elements of UML.
I learned UML in the year 2000 by reading the full "The Unified Modeling Language User Guide" book by Booch, Rumbaugh and Jacobson.
Every time I tried to create a diagram during the years, after envisioning how I would express the idea with UML I was blocked by the tool not supporting the notation elements I needed. Like for communication diagram the tool did not support the iteration notation for message numbers, only simple numbers (what tool was it? maybe even Rational Rose). Or qualified assignation (when association is a lookup by a key).
I adjusted to not expect much from the tools and I think I know how to use UML to create useful illustrations - just workaround the tool limitation with a comment or build the notation element from basic boxes or use a less descriptive notation then I wanted initially.
Not to say I used UML very much over the years, as I use it today I realize I forgot many things and need to refresh my memory.
However, I see sequence diagrams used all the time. From time to time I see other diagrams. The tools like plantuml as well as the online utilities like https://www.websequencediagrams.com/, https://swimlanes.io and https://sequencediagram.org are flourishing.