They also had villain trouble. The go'a'uld weren't hard SF plausible but they were still far more believable than the wraiths. The producers had convinced themselves that the foreign culture costuming of the wraith was stupid and contemptible (like all foreign cultures apparently.) They thought the new villains would be cooler. They were just generic instead. So none of them really had an undercurrent of genuine menace to sustain them as convincing threats, unlike the go'a'uld.
Yes, I agree. SG:A had a lot of trouble figuring out its villains. I actally thought the Wraith had some potential until they were shuffled aside for the frigging Replicators.
And I loved the little twitchy bug-like Replicators of SG-1. They were creepy. But then we had the human-like Reps, who seemed to do nothing but talk, and talk, and talk some more.
Having said that, I still thought it was an enjoyable show. Not wow-great, mind you, but SG:A is a fun way to pass the time.