It is partially. There's some basis in reality since it's actually very profitable overall, but the investment goes beyond reality. I'm not saying you shouldn't invest in tech. It's possible this bubble never goes away.

Valuations are definitely in a bubble

Most of these unicorns simply can't turn a profit with their current cost structures. And even if they do, the profits will be so small that the valuations will simply not be justifiable.

I'm not sure dependency implies a bubble, rather a risk. For companies like Amazon(AWS), there certainly is an element of being too big to fail because AWS and similar cloud operations provide so much of the infrastructure for other applications.

The bubble can clearly be seen by the disassociation of valuations from the underlying value, which for many new companies is nothing.