And what stops these best players from joining the qualifiers? I get the feeling you are too focused on the invites that you forget the other half of the brackets. I personally think it's weird inviting people who may have performed well in past tourneys but haven't touched the game in months.
Of course, you have a point. But there are two things involved here:
1) Those good player's that didn't got an invite. You are right that they can join the qualifiers.
2) Those players that got an invite that doesn't necessary deserve it, and in that way take the place from someone else who maybe deserves it better. By inviting people, there are always the same number of less places in the tournament. Your suggestion doesn't solve this problem.