Roundabouts are great (we just had two complex intersections with traffic lights replaced by roundabouts and the traffic flow is much better), but they take significantly more space than a 4-way stop.

Roundabouts excel when traffic volumes on the intersecting are comparable. They are crap when traffic volumes are highly disparate

A lot of legacy intersections don’t have space for round abouts even in cites that embrace them.

Even rural Georgia has double roundabouts now. Not sure why people on the internet can't contain their glee at stating the US is "allergic" to them when the frequency of roundabouts has grown significantly in recent decades.

Because retrofitting them properly requires emminent domain. The ones they shoehorn onto former four way stops are so useless. They are so tight you still have to face a stop sign vs being able to just seamlessly zipper merge in a proper larger circumference roundabout. When they have room to build out a proper roundabout they are usually OK but that is hard to do outside say new suburban construction due to lack of available land on the right of way.