I'm totally with you on this one. My best indulgence before the pandemic (and about to be revived) is a trip to the opera at Toronto's beautiful opera / ballet house, the Four Seasons Centre.
Although some dressing down is visible, most people still make an effort. I'm definitely there with partner in a casual suit, dress shirt, and a colorful bow-tie which of course I tie myself (because I'm old, I figure I might as well be eccentric, too).
And I'm really gratified to see young people, in their twenties, instinctively getting the unspoken standard, and especially when the young women wear eye-catching party dresses, as though to a gala event. It's so encouraging to see them making a special occasion out of their outing. It sets the evening apart as something memorable, special, culturally significant, something to focus on and bring your best self to. It comes down to respect, in the end.
Clothes impart an attitude. If you're having a photographic portrait taken, for example for work, wear dress shoes, even if it's just a headshot. I guarantee those shoes will inform your image just by the fact of your wearing them.
There are some cities where you just don't slob around, and my frequent visits to New York have taught me that there are some cities where you're on stage when you leave the house, by default. That's what makes people watching in NYC so fascinating.
DR