Why is there no dress code in the Church? There is immodesty and a lot of overly casual dressing for the miracle that takes place.

There is an understandable concern today about the way many people dress for Mass. There are double issues of modesty and also of people attending in clothes that seem far too casual for the holiness of the Mass and of God’s house. 
 
The problem begins as a cultural one. The fact is Americans seldom dress up any more for anything. Even many work places that once featured uniforms and/or suits and dresses, have become very casual. Modesty too is a cultural problem that includes clothes that are often too tight or revealing. 
 
Now culture is very influential for most, often, sadly, more influential than faith. Deep faith would seem to inspire a devotion, and sense of the sacred for the Holy Liturgy and for God’s house. But due to poor formation in many, the influence of culture prevails and most think little of how they dress when going to Holy Mass. Frankly most do not intend any irreverence, but simply dress without a lot of thought. 
 
Thus, a problem in issuing a dress code is that there is a range of acceptable views on clothing. In fact, the word “modesty” comes from the word “mode” referring to the middle of some range of views. And frankly, standards vary across time and cultures and especially regarding age. I have often found that many younger people are surprised to hear that what they wear might be considered irreverent and express a little irritation. Older folks remember different times when standards were different. 
 
That said, a general norm for men might be: trousers, not jeans, a button-down shirt, or at least a T‐shirt with a collar, no crazy slogans. For women, a skirt and blouse or dress at knee level or lower. Women should avoid low cut blouses. Sleeveless blouses are debatable. But in saying this, it would generate a lot of very different opinions. 
 
Hence, perhaps the best we can do is to gently remind all people of the sacredness of the Holy Mass and seek to grow their faith in how special the Mass is. As for modesty, more significant moral issues are involved, but so are greater sensitivities. It is a very delicate matter for a priest to speak in great detail about women’s fashions. Frankly we wish older women would take the lead here, and speak to younger women. Priests and men can speak to younger men, but here too, laymen ought to lead in this manner.