I was thinking along those lines in the first half of my twenties. Now in the second half I feel lucky that I found a topic that I am going deep on and I am using that to go wide in some other connected areas.
In hindsight there was some time where I had to actively force myself to stick with one topic longer than usual to go deep. Once that hurdle is taken I have less of a problem now integrating adjacent topics.
I also agree with the advice that focusing on one topic improves professional success. Long-term is TBD though.
My strategy is to chunk the topics I'm interested in. At least on a per day basis but usually longer, reading several books on a topic, experimenting and taking notes.
Sure, but it's just factual that if you have x amount of hours to devote to projects during the week, the more projects, the less each project gets.
Perhaps some build off each other, but I'm sure you understand every hour of technical writing you do takes away from building an animal sanctuary.
Also, I started to gather a reading list on technical writing not for completely new projects such as books or blogging. But rather to improve how I communicate to my clients and collaborators. In concrete terms I want to write better documentation and specifications for the projects I'm building (typically custom web apps for SMEs).
Then there is also a synergy with my part-time teaching job. Writing better handouts, structuring assignments and so on.
Last year I had a bit of a crisis. I believed that I needed to become more focused on one particular area to facilitate long term professional success. I think I got this advice directly or indirectly from different people at different times.
But I couldn't. I looked at specific areas to specialize in isolation. All of them are interesting, but I could feel almost physical pain from just thinking to narrow down my focus on any of those.
Then I gave up, and what a relief that was. I realized that I'm not wired this way. I see the connections between the things. That's what draws my attention and endlessly motivates me. Tackle a new problem, refine my skill a bit here, bolster my knowledge a bit over there.
Quoting Heinlein: Specialization is for insects.
This resonates with me.
Now I'm a programmer (full-stack web), teacher, consultant. Recently also started learning technical writing and working towards building an animal sanctuary.
I see more and more connections between those things, which is satisfying and rewarding, often in unpredictable ways.