TomI know what it's like to fly in hazy weather. I have flown in plenty of it, both for practice and for airshows and contests. You are certainly smart to be careful watching for traffic! On the other hand, if you can do it safely, it's good training to practice in weather that you might have to compete in. Six miles vis isn't that bad, and if memory serves me correctly, you have to have three at the contest. It's more difficult to see the horizon, of course, in hazy weather, so you have to rely on timing of maneuvers in order to stop on a point, among other things. So, consider it good training for the future.
Best,
Patty