you suggest Doomsday speedblitzes the whole team before Sersi can form a thought. Having in mind that Doomsday has not been shown on paper to move faster than thought and that the Eternals are said to operate in brain capacities much greater than a human, at best I can see DD surprizing two or three members at the strt of the fight. not to mention that sersi along with monica, vision and worbird might start flying and thus DD would go for the ground team first.
Seriously though Sersi only needs a thought and DD is not Flash