But the explosive success of 5E has brought that out, and it's not entirely the fault of the people being snarky about D&D. Some of it is 'eternal september' quasi-nostalgia, some of it is people pushing about against something being popular, but a lot of it is that D&D discussion has invaded all sorts of other places that were either specifically about alternative systems, or were intended to be balanced in what was being discussed. The relative newness for a lot people in the overall hobby, along with Wizards very much pushing it as a lifestyle/identity choice has also resulted in a lot of people discussing D&D on the internet being some mixture of hostile/dismissive/etc. of any discourse that isn't about 5E.

I've lost count of the number of conversations I've witnessed where people are talking about something they dislike in D&D or asking how to homebrew a system on top of it to do a certain thing, and someone will politely say "Hey this is pretty core to how 5E functions and is part of the primary gameplay loop, you might want to look into X system because it handles Y thing in Z way, which seems to align with your needs here," and they get a rather rude dismissal. With the release of the One D&D rules, I saw lots of conversations where criticism of them, even from 5E players, were taken as some sort of personal attack on a core values of people who were fans.

There are plenty of assholes in the OSR, storygaming, etc. scenes. Toxicity sure isn't limited to the 5E players. But the sheer number of them, coupled with the previously mentioned Wizards marketing strategy, has resulted in a lot of the rest of the TTRPG community stuck with their hackles raised and feeling like they always have to be on the defensive. And that leads to the snark.