A lot of the hatred comes from people who claim that MegaForce is being unoriginal, and with how the plot for this season is a giant tiki head and a robot make 5 teens from high school into super heroes with spandex take on an alien force from space, I can see where they are coming from.
However, the problem with that logic is that it's not being unoriginal and lazy, but rather "going back to your roots".
We still can't forget that, despite the success of Samurai, Power Rangers is still recovering. I mean, let's face it! Operation Overdrive was such a failure that most fans gave up on it after that. Those that stayed said that Jungle Fury was better than Overdrive, (Though that's not saying much.) and that RPM was the best Disney had ever done with it. Saban buys Power Rangers back and saves the show with Samurai.
So, they decided to go back to the beginning and use elements from the first season that got it so noticeable and popular in the first place.
Not just the storyline, but also the blue ranger is a nerd again. The pink ranger is the happy-go-lucky girl. The red ranger is the motivational leader. (Though they did keep out the racial stereotype controversy that made it popular in the first place. You really have to love controversy arguments.) They all hang out at a place that is run by a guy named Ernie. (Though a completely different Ernie in this case.) Long time fans will recognize that not only does the black ranger have an ax for a weapon, but also fails at getting the girl despite his best efforts to impress her, much like Zack did.
<sarcasm>I wonder if they'll use the "evil ranger" storyline for the sixth ranger and once he's good and part of the team, he'll go for the pink ranger. Because that SO hasn't been used before.</sarcasm>
So yes, while there are comparisons, this is not being lazy, but rather the writers are just going back to it's roots.
Come on! After 20 years, it was probably time to go back and see what made it popular in the first place.