No, I'm not saying that you should accept someone else's valuation of your contribution. Instead, I am questioning this particular person's valuation because, like those of so many other employees, it is too narrow.

If you do not even address the long-term value you provide to the company, then you can't possibly make a reasonable argument that open-offices are a detriment to that long-term value. For the record, I believe they probably are a detriment, so I have an incentive for the discourse and arguments to improve.