I'm thinking maybe you heard something about the evolution of perfume composition and then jumped to a premature conclusion about perfumes when smelling them. Smell more with an open mind, and you will discover a lot more going on. It takes a little bit of time for your nose to grow, but not like Pinnochio. :)
What is true of modern perfumes are two things related to your comments, having to do with a relatively greater reliance on synthetics (they've been in use for all of modern pefumery), and the relative reduction (not elimenation) of the percentage of natural materials.
One, it is somewhat more common, and somewhat has been popular, to make perfumes with a more "horizontal" minset, having a single scent theme (not so often a single note) that lasts for much of a perfume's life. The defining characteristic of such perfumes is that the ingredients have similar evaporation patterns, so that you most always smell most everything. I'm no authority on what perfumes are currently popular, though.
To complete that thought, a more "vertical" mindset would look at a narrow smell theme, or a "single smell" with top, mid and base characteristics. That view allows you to trace a smell like an unfolding story. A balanced approach is to compose perfume with a balance of a vertical/horizontal outlook. When I plan a perfume, I plan it both ways, which is probably just obsessive-compulsiveness.
A second characteristiic of modern perfumes relates to the greater availability and/or greater number of quality materials, making it easier to use aromachemicals that last as well as having top and or mid characteristics. What that means is if there is an aspect of a perfume you want to last a certain time, there are often options for getting you there, as compared to before in history.
An essential oil or natural substance is a mixture of chemicals with different evaporation patterns already, so it's just harder to have a horizontal perfume. For example, one might suppose of bay rum as a one note, horizontal perfume, since it's typically composed mostly of bay. But really, smearing just bay on yourself does involve an unfolding story, since it's an essential oil. Same with all other natural materials, or most. (I suppose rosewood has more horizontal characteristics due to the linalool, and clove is another example,depending on the variety.). It's easier to find synthetic materials that just are what they are, and it's easier to find more materials period these days, thousands of them.