By whose measure?
"It is the oldest course on the Tour.."
Sure about that?
"... and it is not set up well for Tour play today....
Well, it's not a treeless, personality-lacking stadium course, I'll grant you that. Definitely requires more than average abililty to shape your shots, something not all Tour players do well. Most play right-to-left, many left-to-right, few do both well, something that Colonial requires.
"Which is another reason why none of the top four players in the world are participating this weekend."
Got some support for that, perhaps a quote by Woods, Els, Love, or Singh indicating that that's why they're not playing this week? Or are you just making that up? AFAIK only 1 of them made the Nelson last week, and it's a long-ball course.
Got any idea how often the top 4 actually enter the same (non-Major) tournament (or conversely, how often they don't)?
Tiger Woods, in his only trip to Colonial, finished four over par. Colonial ate his lunch.
The four top players (like the UGLY Veejay Singh) are cowards. They can't risk being shown up.