Interesting. What canned adventures have you tried to run? (as opposed to full-length APs, which are a different breed of animal entirely)It is possible that I've just been extraordinarily unlucky over a similar length of time, but I've never--not once--played in a published adventure that was more than a time-filler, and I've never--not once--been able to make enough sense out of any to run them.
And yes, they're not all perfect or even good right out of the tin - most take a bit of tweaking if only to fit them into your own campaign's settng and-or story. But even with that they're hella less work than writing a homebrew adventure from scratch.