My personal opinion:
We ought to look our best when entering the house of God. Ideally, our outward appearance should be a reflection of our inward disposition. I think this is a very Orthodox idea. Our priests and bishops are vested in precious materials, to be a reflection of the dignity of their office. Our time period is the first in history when we actually prefer to dress down in public. In our parents' and grandparents' day, you wear suits even when leaving the house. I think this went along with the general seriousness they had with life. Our generation does not know what gravitas is. This era has no room for reverence and propriety, which have been set aside for weddings and graduations, etc.. These are the last remaining reminders of an "other world." We Orthodox, and traditional Christians in general, should be the first to correct this aberration in modern society.
Obviously, the poor should not be looked down upon for what they can and cannot afford. But this is something the Church has had to deal with from the very beginning. This ought not be an excuse to come to Church indecently. Notice that the poor still want to wear their best, like the widow who offered her two pennies. An yet we, who can bring ten bags of gold, offer the same two pennies.
The argument that since holy fools and monks dress poorly, we should do the same seems rather absurd to me. We should seek to imitate their humility. Sometimes humility means conforming to propriety. If anyone is inspired to take up the monastic habit, then good for them obviously, but the habit does not the monk make. And over-exaggerated humility is one of the best ways to fall in delusion.