1.3 million backlinks, No SEO - Help ballparking the importance of SEO

I'm in an organization that has been around for a long time and has a website with no SEO. Their site has 1.3 million backlinks but only gets about 2 thousand organic clicks per month. The domain authority was very high (78/100 on the free tool I was using).

The membership of this organization skews (much) older and I would like to help them understand the potential their site has for driving traffic.

I have tried to explain it in writing, then through a video that I made specifically explaining SEO and the opportunity for the site. I haven't heard back all that much.

I cannot ballpark how much traffic a site like this could bring in, let me know your thoughts.

Possible questions:

Would it be pretty easy to bring a million visitors a month if we started publishing articles on the right keywords?

How many articles would you guess it would take to bring in 100k or 1 million visitors a month? Are these numbers too high or too low?

I am familiar with Yoast/RankMath and keyword research - That is enough knowledge to get the ball rolling correct?

I am hoping to share this thread with the leadership and make a real impact!