Basecamp first launched when I was in college, and being completely unfamiliar with any project management workflow I thought: "this would be great for managing myself" so I set milestones and wrote entries for myself and project managed my life for a brief period. It makes life as boring as work. These methods are meant for teams working towards a common objective, where anything extraneous to the OKRs is considered…
That would be an obvious misstep. Both in terms of objective setting and in measurable key results. This blog post misses part of the value of OKRs: they teach us to set high level objectives and repeatedly decompose them. Here, objectives are instead just categories that provide no focus. It's like that antipattern where managers ask their directs for projects then try to combine them into OKRs. What, pray-tell, does launching an open source project have to do with boosting knowledge? And like, why 20 books instead of 10? And why specify quantity rather than quality or subject? Does reading a book mean you've boosted knowledge if you barely remember anything you read?
A better OKR setup would likely be something like (a bit modified to suit my own circumstances):
Objective: Boost Knowledge
Key result: learn more about statistics
etcWhich is decomposed into:
Objective: Learn more about statistics
Key Result: Work through the Freedman, Pisani and Purves Statistics textbook
Key Result: Create a hundred Anki cards on statistics
Key Result: Make the front page of HN with a stats blog post
And even those can be subdivided Objective: Make the front page of HN with a stats blog post
Key Result: Generate ten blog post ideas
Key Result: Research and analyze five blog post ideas
Key Result: Publish and promote all five blog post ideas
But you're absolutely right that meaning can be lost. Moving passion projects into a todo list misses the 'passion' part entirely, and is best reserved for the drudge parts of life necessary to enable the sublime. By all means, set OKRs for retirement, taxes, and career development.