It's all a bunch of opinions, really. I personally found it superb, in terms of action, plot, characters (all of them), setting, premise, and character development, and even with the retool messing a bit with my perfect show, I lived. It's my favorite Sentai now, up there with Magiranger and Jetman, and I'll never get the hate or, probably, agree with or even understand the complaints. To me, it was just that good.
But what can you do? People didn't like it and they have their reasons. A lot of people didn't as it turned out (though I'm of the opinion it did "badly" more because there were no toys or gimmicks to sell) and now we have Kyoryuger, which is amazing so far, so hey, that's also great.