Given how well the three previously all but unknown child actors central to E.T. performed, I accept no excuses. They should have "developed" elsewhere. The same is true of Tom Felton (he's particularly "school play" in Chamber of Secrets), though I agree he and the others did improve as the films went on, and in some cases went on to outstanding work (for example Emma Watson, who I don't much care for in general for multiple reasons, was superb in Little Women).