Using et al. for a last / senior author rather than for a first author Suppose a paper has authors A, B, C, and D. The first author, A, isn't in academia anymore, and much of my work is inspired by the senior author, D. I've also only communicated with author D.

Can I say/write "author D et al."? 

When I looked this up, "first author et al." is the recommended version, but I would rather prefer to say "author D et al."

This isn't for a formal paper submission, but rather for something like a blog post describing my recent findings, which I hope will be published in the near future.
I think in an informal medium like a blog post, you could convey that author D is the main character in the “story” you are trying to tell while still maintaining proper citation standards by saying something like, “Author D and his/her colleagues (Author A, et al., 2018) have shown that...”