Does not scale. If everybody followed this rule ...
You can absolutely guarantee everyone isn’t going to follow that rule so why bother considering it? Also, nothing says you need to keep investments forever, a rolling fund where after X months you sell the stocks and repurchase based on current spending habits could work just fine at scale.
Nobody bought a iPhone because they thought it would appreciate in value.
The trick is to identify products which will be considered iconic, while they're still on the market. This is crystal-ball-gazing, and that kind of game isn't for everyone, but it only takes one smash hit to make a profit on the total investment. There are certainly people who do this as a hobby / side hustle.
The price of other stocks would plummet from low demand
Demand is ideally a function of fundamentals.
The stock price being overvalued is irrelevant if “everyone” is buying it. This is a hyperbolic example but it plays out in the valuation of the sp500 when legions of folks just dump into an index fund.