The fact is the Disney-PR era was deemed to be really bad and Saban's era was better. So let's get down what I think caused it:
When Bruce Kalish took over, there was PLENTY of bad writing. Operation Overdrive stands out for this. Scripts were that short. The only respectable series was SPD.
Starting with Ninja Storm, there were a good number of overacting girls. They were really ruining the whole show. Overacting cast members ruin a good show, the higher the overacting, the more damage done to a script. Bad writing and overacting made it worse. I agree with DancingAlienDude in comparing Disney and Nickelodeon acting. I have to admit that overacting existed in Saban's era of PR or Super Sentai but it wasn't this bad IMO.
During this era, I felt many of the characters lacked development. Take Hoji and Sky for example. Hoji revealed more of plus and minus points than Sky for me IMO. Why? Well Sky as great as he is as an officer with a cocky attitude at the start, his character didn't show much development for some time and just shifts too fast. Hoji was shown to have more personality from the good points (the you're all more important than me personality) to the bad points (like his being cocky and overconfident at times), which makes him more developed for a character as well as some of the tragic incidents in his add drama which shape him up.
I think it has to do with the wasteful way of running things. Just imagine that Tetsu was a real guy, in SPD the Omega Ranger was just a ball of light because they could not hire another actor from too many explosions.