I'm not a Catholic, but it's my recollection that praying to the saints doesn't negate or contradict the idea of God's omnipotence (power). Rather, the saints are intermediaries. They don't do anything per se, but rather are ambassadors on our behalf. It's nearly 40 years since I last took a catechism class, so I might be wrong, but that what I remember of it.
I get it, I was raised Catholic. And you're basically right from what I was taught. I just never was able to wrap my head around even needing the intermediary if God were omnipotent in the first place.