Concur 100%. In my experience across several states, Zs only have a chance at truly being competitive in FP. Other classes will have cars that we can't keep up with, if they show up. It's never fun to be the only car in your class and "win."
Like all forms of racing, one must maximize class allowances to allow the driver a chance to compete. The S30 just isn't a platform for competition against a modern car.
It is however that platform that connects driver to the road most directly. Our Zs are among the most exciting cars to autocross in terms of adrenaline for this reason. Racers with faster times get out of my Z hooting and hollering.
I'm with Jon. I target competing against a few cars or drivers. I prefer to have a passenger than drive alone. Why hog the adrenaline? Get in!
I pursue excitement. I feel like I win, because I'm driving my dream car since I was 17. And that's my best victory, really.