Have you ever seen someone do something difficult and a bystander who is unable to do the same thing will just write it off as being too easy or irrelevant?
There is an attitude among some Internet folks who would like to have people believe that SEO and its related tasks are not important and that SEO itself is not effective.
I guarantee that anyone who says this has never studied the results of Analytics over the course of a marketing campaign and has most likely never used the same Analytics or other tools to give that website an edge over the competition.
I guarantee that SEO is more alive and well today, possible with a few more acronyms, than it was 10 years ago. It is just more complex and because it’s complex there are people who just haven’t figured out how to keep up. These are the people who will try to discount its effectiveness.
If your sales person discounts SEO then slam the door and fire them. They’re ignorant.