The traditional historical PE ratio of ~17 was before it was so easy to invest in the stock market. PAssive or not.
The current SP500 pe ratio is ~31
It's not unreasonable to expect that this might even be below the new average whatever that might be. In fact, the antistock market like gold/silver/bitcoin is also probably low; not high.
Even if 17 is still the correct number, 31 isnt even a bubble by definition.