If Tintoretto and the other old masters were «acknowledging the picture plane» or «acknowledging two dimensionality» by creating an
unbroken surface
skin, and modernist painting, since the breaking up of the surface, initiated by Constable (according to Heron, quoted by Robin in a recent thread), has acknowledged the picture plane
through flatness of the remaining fragments / pictorial planes, then maybe one way forward would be to discover new ways of acknowledging two dimensionality that do not involve flatness.