There is definitely sample bias, but you also have zero evidence which direction that sample bias goes. You have no evidence that the forums contain more unsatisfied players than the general playerbase. The forums are going to be the most representative out of all social media because only players who are subscribed can post, and because all official channels point towards the official forums.
We could agree that the forums have an intensity bias, in that people here generally have more intense opinions because they feel compelled to post in the first place. But which direction is that intensity pointing at? You have no evidence for any of that.
For example:
https://forum.square-enix.com/ffxiv/...y-in-Endwalker
This thread, one of the most major "criticism" thread on the forums (in fact I believe it is the fourth in size out of all threads), got ratioed:
387 likes on the comment saying they liked the story versus the 254 likes on the topic.
There are plenty of examples of negative threads getting ratioed. With these examples, how can you confidently insinuate that these forums naturally slant negatively? The healer strike thread is one of the few major criticism threads that has virtually zero "ratioing". This looks VERY, VERY different from the situation in the EW story thread.