This issue is beyond just the Canadian Open. The PGA tour has taken a strategy to heavily promote its key events as a way to generate attention for its product and hence its lesser tournaments. The problem is that the top players become too busy with the key "must-attend" events, and they then don't show up at the lesse fields. (Basically a poor distribution of stars accross events_
It's not only the Canadian Open has this problem. Heck stellar tournaments such as the Colonial, Western, Pebble Beach, Doral, Byron Nelson have had very weak / average fields lately as well.
If you are Tiger, Phil, Vijay, before the season starts you already have 11 slots fiiled.
1. The Mercedes - All the prior year winners.
2. The World Match Play
3. The TPC at Sawgrass
4. The Masters
5. The US Open
6. The British Open
7. The PGA
8. Bridgestone
9. AMEX (WGC)
10. Ryder / President's Cup
11. The Tour Championship
1,2,3,8,9,11 are all inventions in the last 25 years by the PGA Tour - all hyped tournaments that bring out the best in the world
The players of yesteryear considered courses like the Canadian Open, the Western Open, Pebble as great tournaments. Unfortunately, they can't attend them all anymore.