Didn't know raccoons wore flip flops!!
I take a lot of Target long-sleeve solid color (mostly black or very dark pink) T-shirts on trips, and paired with a scarf and a nice solid-color black skirt or skinny jeans, I look (IMHO) quite presentable. In fact, I've had many people from various countries comment to me that I look very nice, and I'm often surprised they comment about my being so thin (as they say) 'for an American.' So, we may be judged not only by what we wear (as is the case even in America).
For dining in very nice restaurants, I'd stick with the black skirt and wear ballet flats instead of the Merrells.....maybe toss a shawl around my shoulders if it's chilly.
My husband insists on traveling in a navy sports coat (the multiple pockets as mentioned by another poster), and he is absolutely convinced it results in better service. The sports coat then gets hung or placed in the overhead, and then is only used for a few dinners out. My husband's rationale is likely correct, as we have had gate agents look at our seat assignments (after I had been scrambling on line or with call centers trying to upgrade) and ask us if we would not like better seats (bingo!). And, we've often been upgraded to nicer rooms when checking in hotels/inns. We've been served complimentary wine/desserts in restaurants. But, we are also very polite and kind in our interfaces. So, if you wear a sports coat and are a jerk....maybe not so lucky.
My husband does NOT wear the sports coat for daily touring...but we look presentable. We've been allowed to go on an earlier-than-booked Scavi tour at St. Peters, and were able to switch our reservations (on the spot) to a timeframe about three hours earlier at the Borghese (when the sign said they were sold out for 4 days), and we had two local gentlemen in Florence ask their waiter to send us each a glass of wine from their very special bottle of wine (that the waiter explained to us that was a wonderful vintage wine that the restaurant kept just for the host gentleman)........and on and on. And, most recently, we had a rep in one of the airline clubs offer to change our reservations (without the fees) and allow us to keep our business class mileage upgrades (usually not allowed when changing) when she realized we were going to have two down-days in Atlanta (being proactive to avoid an ice storm in Nashville/NY). How one presents himself/herself......the whole package, not just the clothing, matters in one's general success in life. There are exceptions (sure), but generally this is very true. And, one does not need to spend a lot of money or dress uncomfortably to look presentable (again, my Target t-shirts).
Now, in defense of those who travel in shorts and what some might consider 'sloppy' apparel, likely you will also have stories of being upgraded, too.
On the other side of the coin, I do remember the taxi driver at the Athens airport who greeted us with 'hello, millionaires' and then tried to scam us by adding an extra E30 to our fare (before the flat rate airport fare was put in place in Athens), but we very oh so kindly did not pay it (acted like I needed to get more cash) and asked the front-desk rep (who came out to kindly interface). But, that could have happened if we were flip-flopped!!
But, we don't strive to 'dress to impress.' It's just how both of us dress here in Nashville when going out and about, unless we are running to Home Depot or working in the garden (and trust me, you would NOT want to see me in that mode.....nor would people on planes or in other countries).
To be clear: absolutely nothing wrong with jeans, provided you have a nice (think long-sleeve Brooks Brothers type) shirt for a man, a nice blouse or pullover for woman with a scarf or choker, and decent, comfortable shoes.
Now, Norma, I'm going to look out tonight for those flip-flop wearing raccoons!!!! I always thought they just stuck with the same brown/black uniform :)