Modern fabrics wick better, smell less, dry quicker, and keep you warmer in winter and cooler in summer.
Now I will take your word for all of these assertions save one. In my experience, polyesters greatly exaggerate body odor, and tend maintain some amount of smelliness even through washings. That's probably the foremost reason I don't wear synthetics anymore.
I'm not having any of that in my cycling gear. I was a little surprised, too, remembering the poly problem. Apparently they've managed to design fabrics that don't retain and exaggerate odors like the old stuff did.
