[optymizer]

I don't think so.

The way I understand the "appeal to worse problems" fallacy is: "Y is worse than X, so why work on X if we haven't solved Y yet?"

In this case, I see X as a solved problem (perfectly appropriate Sans Serif typefaces exist) and Y as unsolved, whereas the fallacy treats both X and Y as unsolved.

[dragonwriter]

So its appeal to worse problems masked by false dichotomy (solvedness is a continuum, not a binary state)?

[zbentley]

I'm not the parent, but now you have a disagreement (it's not solved; solvedness is a continuum) not a fallacy.

I don't think it's in good faith to assume that because parent said "perfectly appropriate Sans Serif typefaces exist" that the implication is that solvedness is a binary; the implication could just has easily been that the problem is sufficiently solved so as to not matter, which is a disagreement about where to draw a line, not an abuse of logic.