God is more concerned about where their hearts are than what their style of dress and what instruments are used.
I’m not omniscient, to know what God would prefer, although I think we all have assumed it, including myself. I know my opinion fluctuates a little on this, but since the subject was brought up again, I’ve given it a little more thought.
For me, ultimately, even though I probably will never truly know what God is really desiring of us when attending mass, it’s giving God our personal best in all things, or at least trying to give our best. To not do so, for me, would make me feel like I’d be insulting Him who had blessed my life. I know the level I’m capable of with my own talents. I will not give only half of it when showing my love for God or worshipping Him. If I only give a half-hearted attempt with my talents, perhaps the people wouldn’t know, but I know that God would know.
That’s how I feel about sacred music. If the parish is truly giving the highest and best of their talents, then there isn’t much more to ask for. But if the parish/pastor totally ignored the best in talents of the parish and made a concious choice to only use and employ less-than-stellar talent to pander to one’s tastes or other people’s tastes or to influence the younger parishioners, I think there is a problem. My generation was subjected to that and many of us have in a way, “suffered”, because of it. Catholictrain brought up a good point with the use of a “High Mass”. In my diocese, at least, I’ve been seeing more of these masses, usually at their 11:00 or 10:30 masses. My parish has been doing it for years and years.
In terms of clothing, if I have clothing in my closet which would be perfect for a garden party, nice dinner, or an afternoon wedding, I will choose my skirt and blouse over my comfortable jeans and t-shirt. Why? For me, it’s because that would be my personal best and thanks to God - the respect and awe and honour I have for Him. It has nothing to do with what other people would think - at least for me anyway, as I have always been an oddball and marched to the beat of a different drummer, as my mother would say.
At the same time, I will not judge those who dress in jeans and t-shirts. I don’t know what they’re thinking. I’ve attended mass at my little country, farming parish where I spent half my childhood. The people there aren’t well-off. They all wear clean clothes, but for some, their best is their cleanest pair of jeans and a button-down shirt.
Of course, I’ve encountered those who are just very lacksidasical about getting dressed for mass too, and those where you wonder where their mother or father was when the teenage girl came out of her bedroom on a Sunday morning.
God would prefer this over a well dressed-classical music-perfect conformity to the rubrics-congregation of hypocritical snobs.
Come now - I’ve known and worked with just as many hypocritical “reverse snobs”, some even rather vehement on the other end of the spectrum as well.

And actually, the majority on BOTH sides can be and are rather loving and good people - just with different ideas. So let’s not stereotype.

I always use my grandmother as an example. She was what some people would consider “blue collar”. She always had an “idea” of what the Fine Arts were like and the people who took pleasure in it, and without really getting to know the people or those arts made up a stereotype of those people. That was until her granddaughter (me) got into it and she began to attend my recitals, concerts, operas, etc. and started meeting the people within my “circle”. She realized that most of us were just average, down-to-earth, and sometime odd-ball people. Of course there are some divas or snobs, but they aren’t in the abundance that some people would have them out to be. And now, she loves what she can with it inside and outside of mass.