[lucideer]

Not sure why you're being downvoted, I completely agree. This is absolutely something that I think should be in core.

There are some features that are rightly being removed from core in favour of being served by an extension (Container Tabs is a great example—one of my favourite and most-used features personally, but I prefer it in an extension for a few reasons). Better tab management is the opposite: this is something Firefox should work on getting right out of the box.

I get that unless/until it makes it into core, we need good, working, popular extensions to bridge the gap, and perhaps to convince core devs there's an audience, but that's no reason to stop asking for it.

Would also recommend people trial Vivaldi, or even Opera 12 (probably still downloadable from somewhere out there) to try out the general UI concept.