Let's see... The First Doctor's attire was fairly formal gentleman's wear from an earlier era. The Second's was like a shabbier, more disreputable version of the same thing. The Third dressed like a dandy, with frilled shirts and fancy jackets. The Fourth's ensemble was eccentric and "Bohemian." The Fifth wore cricketer's whites with a coat and fedora. The Sixth was in a garish parody of formal dress. The Seventh had kind of an eccentric-professor look with the cardigan and porkpie hat. The Eighth went back to a retro, anachronistic look that was sort of a blend of First and Third (wasn't it basically a Billy the Kid outfit that someone was going to wear for Halloween?). The War Doctor had a heavy leather coat, a cravat, and a waistcoat, sort of an old-timey adventurer's look. The Ninth had the most basic fashion sense, just a sweater (jumper) and leather jacket. The "suit" trend was really just the next three.
Okay, I guess you could say that the early Doctors' outfits were variations on a "suit" principle, but the difference is that they were from a time when it was still pretty routine for men of their age to wear suits on a daily basis. A suit doesn't have to mean formality and polish -- lots of frumpy, disreputable characters wore suits, e.g. Lt. Columbo or Carl Kolchak. It was the quality and neatness of the suit that differentiated between formality and frump, businessman and working man. So, yeah, I guess the same goes for the various Doctors like the Second, Tenth, or Eleventh.
