B737 Captain reported a spacing issue with several aircraft and had jet wash from two departing aircraft while on short final at SFO.

Narrative

We were given a visual approach to Runway 28L. Approach Control paired us with a 757 which we were faster than; given 180 kt. to bridge. As soon as we changed to Tower they told us to slow to final approach speed. They put Aircraft Z on the runway and cleared them for takeoff. No sooner did they do that they cleared an Aircraft A heavy to line up and wait. Told him we were on a 4-mile final; barely cleared them for takeoff. As we continued approaching runway; we at 200 ft.; they were just starting to rotate. We had a lot of wash from the double heavy takeoffs. FO did job of correcting and landing plane. A miss would have been mess with a plane on the right; a heavy that just took off; and a heavy rotating. No reason for the spacing issue that was created by the Tower.