I just want to suggest that a literal messianic age on earth is not in itself wrong; in fact, it is right. The "utopia" at the "end of history" which Marxism and other materialistic philosophies tout is not Messianism, but a secular perversion of Messianism. G-d could have created a purely spiritual world but chose to create this material world and put us in it. This means that this world, and not just the higher spiritual worlds, must eventually be sanctified and brought under the Kingdom of G-d. The notion that it is nothing but a "waiting room" for a heaven of disembodied spirits has in fact defaulted this world to the atheists.
Please note that in order to bring about this Messianic era, G-d's directions must be followed. There is no other way other than the one G-d Himself has communicated. Any G-dless plan, or heretical plan, will fail utterly.
While it is true that man's evil inclination has been dominant since the sin in the Gan, eventually it will be sublimated under G-d. This is not naive atheist optimism. The G-d who created this world will bring it to fulfillment. Nothing remotely Communist about it. Mankind began its existence in a paradise. That paradise must be restored and G-d's creation vindicated.
Also, note that the idea of a future paradise on earth is present in Catholicism as well; that's what this whole thread is about. What is the "triumph of the immaculate heart" but a Catholic earthly utopia?
We agree.