When to Repair Versus Replace Concrete Slab?
It's done-for. Whenever you have both severe surface degradation and spider cracks there's no turning back time. No patch will hold up with so many independently-movable segments. You'd have to pour a new slab that's robust enough to span such movement.
If it didn't cause problems at the door opening you could lay paver bricks over the top. They'd do pretty well I think. That would mean doing the same out into the driveway, though.