I find modern tokusatsu seems to put more effort into making the gimmicks each year wildly different, while stories are often a bit more samey. Not from year to year, but typically you'll see the current series reusing a mish-mash of story ideas from shows made roughly two-to-five years ago.
I think the older 80s shows put a lot, lot more effort into more original storytelling than their modern counterparts, in part because they couldn't splurge tons of money on wholly different effects each year. It doesn't cost more to make your script good, though, or your plot twists compelling.