Those that are wearing "current" high fashion are usually keeping up with it. Those that can't afford the constant change are usually wearing simpler items that are less obvious as out-of-date. The short gown worn by lower classes in the early part of the century is a good example of slow change. There will always be examples of those that are a bit dated or choose to wear the more conservative fashions (today we call that a classic look). This image from 1827 has a man wearing breeches, something still sold and advertised, but certainly not up with the latest styles. He's meant to be a bit of a country bumpkin and seems to be behind the times.
As for vintage styles, you do see major inspirations from previous times in fashion. 1790s took from the Greeks and Romans. 1880s took from the 1780s. Though they make fun of older styles that aren't back in as well. A print from 1827 shows a very inaccurate jest at 1757 fashion. This is from a post on cyclical fashion I commented on:
There is definitely some cyclical nature to older fashion. If you want to get very detailed you can find it constantly, but the large scale repeating happens less often. For example, you can see ribbons tying shoes in the early 18th and late 18th century, but between 1720 and 1785, buckles were popular and ties were for those who couldn't afford them. Small, but short term repeat. Long term we can look at the bum roll and farthingale popular in the later 16th century. The hoop that came into fashion circa 1700 began as a shape similar to a farthingale and eventually changed into an oval by the 1720s. The bum roll reappeared in the 1780s, still very close in shape to the original.
But, keep looking and the hoop appears again in the 1850s as the cage crinoline, eventually changing shape into the bustle. The bum roll also makes a come-back in as a bustle pad.
Other styles come back around because of sudden popularity of the time period, such as the trend for late 18th century styles during the Centennial. The Polonaise being a perfect example of this.
