Your argument, while valid, also kind of misses the point of the original post: to know where your career ends, you also have to know what the general trajectory looks like. Basically, you cannot "coast" ever upward "naturally" anymore, because we've learned that's a bad concept (hence the term "failing up").
We pressure people into management roles who have no reason being there other than "that's where more money is" or "that's how you create change". If someone's "end state" is a highly competent and flexible IC, then why isn't there more money for them to continue succeeding at that role as compared to an ineffective manager? For all the talk that tech is a meritocracy, it obviously isn't, otherwise we'd be rewarding the best talent without forcing them into bad roles or hollow titles.
Motivations aren't restricted to money alone, either, as we've seen post-pandemic with the WFH-RTO conflicts. A plurality of workers have realized their time is more valuable than their work, and are refusing to take chump change for multi-hour commutes from affordable suburbs just because their employer is arbitrarily demanding butts-in-seats in a pricey city. Others want their employers to be more involved in politics, or at least acknowledge that choosing to be a for-profit business is in fact a political statement in and of itself; hiding behind faux-neutrality in times of crisis isn't sufficient response anymore. The times are a changing, and the workforce is increasingly making its frustrations known.
Which brings me to your last paragraph:
> ...for most techies, the most useful goal is to make money fast in a way that doesn't drain your life energy.
I would like to proudly stand up as one of those not in that "most techies" crowd. I do this work because it comes easy to me, is incredibly interesting, and allows me to work in infrastructure in a way that isn't building roads or laying pipe. I identified my career ending way back in High School: acting as the jack-of-all-trades IT guy for the school or district, grey hair and hoarse voice, gradually nerd-sniping the kids who, like I was, are bored out of their skulls and looking for a challenge. The money certainly helps (even if it's not nearly enough to buy a home close to the office), but my career begins and ends in ultimately the same place.
And that's the point of the post: identifying where your career ends, and the arc it takes to get there. It's why I'm doing the leadership courses and trying to beat a new path upward in the corporate world, one where highly-competent ICs who are also good leaders are recognized as such and put into long-term positions within an organization, to weather the storm of cyclic leaders and fickle shareholders, and ultimately build a stronger, successful, and sustainable entity as a result. I need those years/decades of leadership and money to reach that position where I have a paid-off home, decent retirement savings, and can finally dedicate my remaining time and talent toward building a better future for the next-generation of people.