We don't know how well cyanobacteria fared against its microbial competitors, how efficient the early photosynthetic pathway was, or how large the oxygen sinks

We don't know how well cyanobacteria fared against its microbial competitors, how efficient the early photosynthetic pathway was, or how large the oxygen sinks were pre-GOE saturation so we have no idea whether planetary oxygenation actually needs to take that long. Without an existing biome that captures oxygen or large bodies of water to dissolve oxides, the process can be many orders of magnitude easier (especially since Mars' atmosphere will take significantly less volume and we might be able to survive just fine with lower air density with a higher concentration of oxygen). It's extremely unlikely that we can pull it off in a human lifespan but I would bet that planetary oxygenation is possible given a few millennia