No, it's not just about "market timing". You can do everything "right", and still lose money. Long-term buy and hold investing is not a guarantee.

An entire generation of young investors has never lived through a serious market decline, and have only been rewarded for HODL. HN skews young. There are a lot of people here who are going to find their worldview painfully challenged when the market does finally turn.

The surest sign of a market bubble in an asset is when I find myself arguing with people that yes, the price of the asset can indeed go down.