Hm. Had a skim through the article and I hit this:
And it is unclear whether a spacecraft could even be launched successfully through the debris shell to enable travel to other planets. Humans would effectively be trapped on Earth by space junk, with multiple tonnes of vaporized metal being added to the upper atmosphere every day through re-entry^12.
This is a common misunderstanding of the scale of space and the scale of how much debris a "Kesseler syndrome" would entail. I checked the article referenced at the end and it was only in support of the "vaporized metal being added to the upper atmosphere" part of this statement, not the "trapped on Earth" line.
We would not be "trapped on Earth" by Kessler syndrome. The debris is only a problem for something orbiting within it, exposing it to continuous risk of collision for months or years on end. Simply passing through is very unlikely to damage a craft.
So an alarmist misunderstanding was inserted into the middle of this article without any reference backing it up, which makes me dubious about the rest of the article as well.