a) No evidence they are dying. All we have is a single quarter's result i.e. statistically meaningless.
b) No evidence that staying true to the original Facebook is the best strategy. Unquestionably, Stories has been a popular feature in both Instagram and Facebook ecosystems and perhaps certain features from TikTok will be the same.
But there is plenty of evidence that the opinions of HN, Reddit etc. often do not match that of the broader public and so should be taken with a grain of salt.