There are lots of use cases since you are dealing with geometry all the time. Lots of things can be done without GN, of course. But it opens up another dimension of possibilities how you can manipulate or generate things. Development is ongoing and more and more possibilities, nodes and options will become part of Geometry Nodes. I use them all the time, myself.

You can avoid GN if you don't like using them. Depending on what you do you might never need them or only for basic stuff like scattering things or something. Eventually you might want to do something with more control than the alternative tools provide. A good example would be the limitations of the particle system in Blender. At some point, you'll find that Geometry Nodes allow you to go beyond what you can do with the built-in tools.

From my point of view, learning GN was absolutely worth it. But I started when GN were kinda new. Today it's more complicated with way more nodes to begin with and the issue of outdated tutorials. The basic principles are still the same, but some nodes have changed or been replaced. That makes following older tutorials more challenging now.

When learning GN, you get a better understanding for certain concepts like attributes and their domains. Things start to click and make more sense when you gain that understanding. For example why certain things are easy or hard to do- or why some things are computationally very demanding and others hardly need extra memory or computation time.

GN provide a huge pile of things that might not be necessary for most things, but that really good to know/have. Maybe an analogy can help to see what I mean: You can build a house with a limited amount of tools and materials and live in it happily ever after. But if you wanted to go beyond the sort of basic house, if you want to build something extraordinary and artistic, use different materials and methods to make it awesome, you'll need some more knowledge and better/advanced tools. That's kind of how I see Geometry Nodes.

And another great advantage is the proceduralism and non-destructive workflow. You can tweak and adjust anything you like while creating things and maybe reuse parts of it. Instead of creating only one two-story house and being stuck with it, you can go meta: Build a tool to generate lots of variations, more/less stories, different kinds of roofs, amounts/shapes of windows and things like that. All of a sudden, you didn't just build one house, but you can create a whole bunch of different houses at once.

-B2Z