I consider myself a full stack developer; have so for almost a decade now - top line of my resume and is generally specifically why people hire me.
I'd add to your list, specifically:
Ability to fire up a server, install software, patch it, monitor log files, etc... (not sure that falls under DevOps)
Ability to price resources - when asked, should we go with Rackspace or AWS, could you answer that? When asked, should MySQL be put on a dedicated server for security reasons or is a Cloud server good enough - can you answer that? When asked, should we stay with PHP or switch to NodeJS, do you know enough about development that you can research the pros and cons of both and present a valid answer - unbiased?
So... you may not know CSS - can you at least write the basics? .container { background-color: #db5132; } ? You may be a strong backend programmer but struggle a little with HTML. So long as you can get by; know how to find the answers you need when you need them - i think your fine.
I don't design, period. I wish I could but I just don't think that way. I can't start with a blank piece of paper and layout a multi page website. But I can buy a template and bend it to my will, putting the customers logo in it, changing the colors and re-working pages to do what the customer needs it to do. I can take a PSD or AI file, slice it up and turn it into a website. But I can't start from a blank state and say "this menu bar should be white text on beige" or "this main body content should be 600px wide". If you told me that's what you want, I'll make it happen, but to come up with it on my own - no. So my strongest full stack developer skills are pricing, stack research, server, sql, backend code, testing, resource monitoring, optimizing, html, css, js, etc... I just don't do the design part.
A jack of all trades still has 1 trade they enjoy the most and excel in.