I think part of the problem is simply that people confuse "was," "were," and "is" with automatically being passive, when they are really just "weak" in a lot of cases. I confess that I was absolutely guilty of thinking that way for quite a while (and I lapse sometimes). It is really easy to mix up the construction with the words themselves since they are linked to the passive form.
Sometimes a verb needs to be weak. In one of the examples above I noticed a change that turned "was wary" into "feared" which are not the same sort of feeling at all. There isn't really an active way to be wary that I can think of right now, but maybe someone else can. Worried is the closest I can think of, and even that seems a bit much.
Maybe it would be useful to point out to people just starting to comprehend the passive vs active thing, that you can go and grab a random chapter of a well known book and you will probably find "was," "were," or "is." Some might be passive, some weak, but even respected authors use both sometimes.
Someone said active should be used when you're concerned with the actor and passive when concerned with the subject. I would add that active can also be about the act itself, while passive is about the effect of the action.
For example, if someone is walking along a road, you might write, "Trash was dumped along the road." Not only does that keep the focus from whoever dumped the trash if you actively showed it happening, but it keeps the trash from drawing too much attention itself. The trash is not really the important part; you don't describe its details or dwell on it or anything. What is important is that this is the kind of place people dump trash. There isn't always time or need to be active and turn it into, "He batted at the swirling papers scraps and kicked a few old, discarded bottles." Maybe the guy is busy doing something else.
One day, I will learn to make small posts. I'm going to make a great, rambling old man.