I agree with this to an extent. The land layout and squarish shape are good, but I don’t think having land entrances from Main Street would be a good idea, simply because it gives you less control over how guests experience the park.
In Disneyland, almost every land has a major entrance and a major exit. For instance, Adventureland has an entrance in the Hub and an exit into Frontierland. The only possible ways for guests to enter the land are from the “entrance” and the “exit”. By adding more entrances, you can’t control what the guest sees as he enters the land.
And without Main Street leading exclusively to the Hub, you lose the “grand entrance.” Instead of walking up MS to the castle, you could turn off of it and go somewhere else. It diminishes the effect, and to an extent makes the park more confusing to navigate.