Most arguments are not logical syllogisms, and their validity tends to rest in assumptions about what is doable and what tradeoffs are worth it and so on that vary circumstantially, so agreeing with it in one case and disagreeing with it in a different case usually means you think the underlying assumptions that give it validity are not the same in both circumstances. Few people are "make your own" absolutists.

There are plenty of differences in the DnD case vs the AO3 case and anyone who thinks those differences are material to the "make your own" argument would use the argument in one case and not the other.