Even now it lacks a lot of necessary APIs that the old one had - such as the ability to disable ctrl+q on linux. I would argue that only around now the new model became usable.

> Making it a more secure

In expense of usability.

> wouldn't play YouTube

It played youtube before and it would still play it without the switch.

Regardless, the old extension model was not the only power user feature which they killed (rss and panorama were two others).