Because it's no longer true. It was for a fair while in the 90s/00s, but every single one of the 18 players who played in the test series v India that just finished were born in England.
And that went well! Bring back the forinners!
(Not "half the team" by any means, but Stokes and Archer would, probably, be first XI picks, and both come under the "born overseas" banner)