In photography, how should we view "cropping"?

I am a beginner. In my shooting practice, I regard cropping as the second most important means of composition adjustment.

In actual photographic practice, however, I tend to be a rough sensualist. I don't always stick to conventional aspect ratios (such as 3:2), because within those ratios my frame always seems to contain unnecessary elements. As a result, I often use free cropping and don't care much about conventional aspect ratios. After all, I figure, except for commercial or sports assignments, how would anyone notice the difference between 3:2.6 or 5.3:3.01 and a standard aspect ratio?

Nevertheless, I am still unclear about the relationship between aspect ratios and visual communication — a subject that books do not emphasize either. What books do mention are some general impressions different aspect ratios give; for instance, 1:1 can convey a sense of solemnity and harmony. But they never truly discuss what an aspect ratio actually means.

Therefore, my questions are:

1) Is it appropriate to use cropping as a means of secondary composition?

2) Is there a truly significant difference between free cropping and cropping to conventional ratios? If there is, under what circumstances is free cropping not recommended?