Yea but, I think its a bit misplaced to be angry at Google for this. Surely its the content creators that place the ads in their content to blame for this.

I don't understand why they ads are not spliced into the stream. It would be undetectable by extensions at all.

Because ads are auctioned in nanoseconds. This isn't the newspaper were everyone saw the same as which was vetted by the editors. You are seeing different ads than your neighbour. Everything is automated to cost as little money as possible.