It is not a roundabout because the traffic on this way has no right of way and all traffic_signs are not there.
See:
https://wiki.openstreetmap.org/wiki/Tag:junction%3Droundabout

junction=circular can be correct.
Most mappers do not add this tag because it has no meaning to the car-drivers. Notice that drivers on the junction has no right of way.  All traffic from the ways to the junction has right of way.
Also the length of the way suggests nothing that it is a circular. The length of the way suggests it is a normal way as one of the sides of a square.

See: https://wiki.openstreetmap.org/wiki/Tag:junction%3Dcircular