"Bundling extensions" sounds to me like a poor description of what I think is the right idea, which is to incorporate things that can currently be done with extensions into the browser in a simpler way. As time goes by it seems like more and more extensions are required just to replace functionality as Mozilla removes it. On upgrading to 115ESR for instance, which has just made it to Debian stable, I find that I need "New Tab Homepage" in order to continue having new tabs be a blank page with a dark background. Other extensions that I think would be worth including as basic browser functions include "Disable Page Visibility", "Disallow console.clear", "Redirector", "RSSPreview", and "SuperStop". That's not counting things I haven't found extensions to replace such as disabling select events, or various simple UI customizations that can now be done only in userChrome.css, requiring additional steps to maintain them with every upgrade. There are also more complicated things like some features from JShelter which I think would also be deserving of inclusion. And of course as mentioned in the article, the always popular "vertical tabs" although I don't care for it myself.

They've cluttered up the UI in this new ESR release with a bunch of redundant "Can always read and change data on this site" text reminding us all of the security risk of having lots of extensions from a variety of sources any of which could one day sell out and turn malicious. There exist at least some "power users" who do not appreciate having to so frequently add new ones just to maintain existing functionality and to do what seem like very basic and essential things.