You'd have to prove these things are possible in the face of the ingenuity of the entire adtech industry. The limitations you point out, on the other hand, have easy solutions:

* auth: Look at https://github.com/kr1sp1n/awesome-gemini#services Tons of services support some form of auth.

Edit: https://martinrue.com/station is another service I use that's missing in the above list.

* images: click to load

Janky but doable. Janky is the price you have to pay to avoid adtech.