Any competent thinker should be able to structure an argument and present it in written form, that's an important skill to have.
If someone is unable to write an essay arguing something, unable to articulate complex thoughts and back them up with evidence, what does that indicate about their thinking?
I don't write essays either, but I'm sure I could. And maybe some of those docs or emails I write at work are made more effective by that.
There are literally hundreds of millions of people in the Anglosphere who have graduated from their education unable to coherently structure an argument and present it in written form.
It indicates nothing about their thinking. One of the smartest people I've known left school at 14 and couldn't read or write.
We mistake education for intelligence often. We mistake erudition for capability often. The thing you need to get a PhD is not intelligence, but the ability to follow directions and persevere. You certainly don't need to have any original thoughts, in fact they will only get in your way.