> You are copying what active investors (in aggregate) are doing so if they’re fueling a bubble so are you.

The "in aggregate" is doing some heavy lifting here. Active management holds concentrated positions in certain investments because they think they will outperform. Active folks believe they have found market inefficiencies, whereas passive folks lean towards the market being (relatively) efficient (enough) and chasing returns won't work (at least for most people):

* https://en.wikipedia.org/wiki/A_Random_Walk_Down_Wall_Street

"Active" and "passive" exist on a spectrum and are not binary:

* https://rationalreminder.ca/podcast/133