Commercial Captain reported conducting a go around on short final due to departing traffic still on the runway which resulted from ATC's inadequate traffic separation.

Narrative

During a visual approach to Runway XXL at ZZZ at approximately XA10L; at approximately 350 ft. AGL a go around was initiated by my aircraft to avoid a Runway landing conflict with an aircraft that was just beginning a takeoff roll on Runway XXL.As my aircraft passed thru 1000 ft. the Tower Controller issued a takeoff clearance to a Company X aircraft to depart Runway XXL. As we proceeded in a descent towards the Runway below 1000 ft. I was unable to visually identify the Aircraft X lining up on the Runway. As we approached 650 ft. AGL I was able to identify the Aircraft X in the over run or stop way of the Runway. I made my 500 ft. foot call at 600 ft. and at that point I focused my attention on the Aircraft X that I could see had just begun it's takeoff roll. At approximately 400 ft. I determined that adequate clearance with the Aircraft X on the Runway could not be assured if I had allowed the First Officer to continue the approach and landing. At approximately 350 ft. AGL I announced on the frequency that 'Company Y is going around'. At that point I could see that the Aircraft X had not accelerated enough to have crossed the Green Threshold Marking Bar of Runway XXL. I felt that the closure rate with the Aircraft X that had just begun it's takeoff roll was unacceptable. During the initial go around we made a slight right turn away from the Runway. The Tower Controller acknowledged the go around and issued a 1500 ft. climb limit. He then issued a turn to 120 degrees and a 3000 ft. climb limit. As my aircraft was climbing thru approximately 1000 ft. I looked left to see the clearance with the Aircraft X. I noticed the Aircraft X was in close proximity to my aircraft at the 10 o'clock position as the flight paths were diverging. In my opinion the Tower Controller was attempting to 'squeeze' a departing aircraft out between arrivals. He should have allowed more time between Runway movements. His attention may have been divided between too many tasks to recognize the conflict he was creating.