No, it's not weird. But it does raise the question of why because they're similar in a lot of aspects, made by the same company and not all but a lot of the same people. If the reason is simply because 'Rider is more serious and mature' then clearly you just haven't seen enough of Rider and enough of Sentai.
I was like that too, for admittedly shallow reasons. I just couldn't stand the five brightly colored spandex suits, and I dislike their roll calling, pointing out that it's stupid and took too long. Then I saw the Shinkengers in the Decade crossover episode, and four years later, now I love Sentai, at times more than Rider. Rider still holds a special place in me because I loved the basic concept so much, but in execution and quality of product, Sentai is miles ahead of Rider.
While the early Heisei Rider shows tried really hard to be "realistic" and more "believable", Sentai(or the people making it) realizes what it is and knows how ridiculous and over the top everything it's doing. But it embraces it and is determined to have a blast with its insanity, leaving all pretension of being "real"(okay, there are certain amounts of plausibility for you to buy into the world, but really, in the end, Sentai's just crazy).
I guess it's a bit of a foreign concept, because western entertainment is so fixated on trying to make everything "realistic" and "believable", and aims to convince the audience that everything it's doing is representing the world and reality. I believe it's a difference in principles called "presentation vs representation". Sentai just aims to entertain and wow you with its outrageous presentation, instead of trying to buy you in by representing the "real". Just keep that in mind when you're watching Sentai. You might start to enjoy it a little bit more.