I haven't got a clear argument that I can communicate but I'm against the idea that all generalists should aspire to become specialists eventually.
I feel like a really experienced generalist can be an amazing team member who can be 'the glue' between the other disciplines on the team, learning to do what is necessary rather than just sticking to what they have chosen to focus on.
As a designer of 12+ years, I honestly think I'll always be a generalist and I'm ok with that. My work may go hidden and I may not push the industry forward by writing and speaking, but I may be able to do it by quietly creating great products and services.
Or maybe I'm just afraid of pushing myself.
Here's the Truth
more like: "here is what I subjectively think".
I say do what you enjoy the most. If you don't know what that is, keep trying new things.
As a designer, you should never worry about being a specialist or generalist, your main concern should always be to thrive as creative as possible, that will make you succeed in the field.
I took a poll in 2017 asking designers what they classify themselves as. Only 20% of respondents identified as visual designers or pure researchers. Interaction designer was by far the runaway favourite. It's actually the LEAST specialized of the disciplines due to the nature of its core tasks — compositing visual design and research together in to flows.
All very useful skills, btw. I'm not really convinced you can't be great at all of them.
"Ignore all of the dumb terms for a moment and let’s focus on the real question: Should I focus on being good at one thing, or should I try to be good at all things?"
Well, that escalated quickly.