I don't think spirals vs regular flat blades has to be an either/or proposition. Blades are designed for specific applications. Spiral blades work very well for certain types of projects, in certain materials, because that is what they are designed for. If one doesn't make those kinds of projects, then there probably is no good reason to use spirals. I use both, but only use spirals where they are the best option. They are not my go to blade for general scroll saw work. I don't think they are well suited for a lot of things, but are perfect for some.
As for the learning curve, I've known several very skilled and experienced scrollers who never got the hang of spirals and didn't use them. It doesn't always come naturally to everyone, but there isn't anything wrong with that. I maintain that, with some practice, any scroller can learn to use them, maybe not love them, but be capable of using them. It's up to the individual as to whether or not it's worth the effort.