The birthrate started crashing long before Japanese animation became "anime," let alone the sort you're worrying about: https://www.macrotrends.net/countries/JPN/japan/birth-rate (although Go Nagai isn't exactly a model of rectitude).

As for the history of anime and what you're worried about Dragon Maid normalizing, let me just point out as an extreme example that Kodomo no Jikan was aired in 2007 a full decade before Dragon Maid.

And I find it curious that you don't seriously consider the arsonist's claim it was for revenge from his perception that the studio had ripped off material in a novel he submitted to them in the light novel competitions they'd started running (no good deed goes unpunished).