What's so hard to understand? I shoot my advertising work at f/8 to F/16 with a 5D3. Clients like their customers to get a clear view of their product, not some arty blur.
What I found hard to understand was your opening blanket statement:
Full Frame and mirrorless don't go together.
If you'd said, "I
have no use for a FF mirrorless camera because I
only shoot from f/8 to f/16," that's one thing. But as far as I'm concerned, FF and mirrorless go together like peanut butter and chocolate. Now, maybe you're allergic to peanuts or can't stand the taste of chocolate, but that's not true for everyone.
Some folks like arty blur, and find documentary images shot at f/8-f/16 quite boring.
Thin DoF and 'arty blur' aren't used in advertisements?