Let's compare to the Darkness spell.
2nd level, range 60', Concentration up to 10 minutes.
Magical darkness spreads from a point you choose within range to fill a 15-foot-radius sphere for the duration. The darkness spreads around corners. A creature with darkvision can't see through this darkness, and nonmagical light can't illuminate it.
If the point you choose is on an object you are holding or one that isn't being worn or carried, the darkness emanates from the object and moves with it. Completely covering the source of the darkness with an opaque object, such as a bowl or a heIm, blocks the darkness.
If any of this spell's area overlaps with an area of light created by a spell of 2nd level or lower, the spell that created the light is dispelled.
So now let's compare:
The spell automatically extinguishes all light sources, mundane and magical, and prevents them from being re-lit during the effect's duration.
Question: What's the radius? What's the duration?
Comment: Mildly stronger than darkness, in that non-magical light sources need to be relit.
Comment: Weaker than darkness, does not do anything to light sources later brought in or ones that were not lit and now are - is this correct??
Comment: Mildly weaker than darkness, not mobile.
Comment: Much stronger than Darkness if there is no limit to the magic light it can extinguish.
Comment: Really stronger than Darkness as this can do things like put out a flametongue or a sunsword. Basically any magic item that needs to be activated and sheds light as a priamry purpose or a byproduct.