Because we’re persisting with a system that requires proper wingbacks to function effectively, which we do not have. The alternative is, therefore, a flat back 4 with 2 defensive midfielders sitting in front to protect them, and 3 midfielders in front of them to provide some attacking penetration and width to feed the 1 up top. A simple 4-2-3-1 as proposed by @joewarkfanclub above.