I can't believe I'm about to say this but the miata endurance race was one of my favorites, and I love miata's. I used to be like you, I used to hate the miata, and I actually still make fun of people who enjoy driving low horsepower slow cars, especially Kei cars (I mean seriously, you got to have a boring life if you prefer kei cars over supercars like some people do) but the Miata is legit. PD has no shame about their car selection though, no other developer is anywhere near as biased as they are. I like the miata but just not enough to justify there being more than 10 in gt5, PD is crazy biased about all Japanese cars.
It's rear wheel drive and light, with a short wheelbase. That's a good combo. It's one of the most fun cars to drive with below 200hp besides a lotus or caterham. In iracing, its the car you start out with, and its tons of fun there. The spec miata series is great.
Seriously, if you still don't like miata's, get the first DLC car pack. The MX 5 Touring Car is probably the best in the entire pack, no joke. Or take the newest miata in the premium dealership, and tune it to the max. If you don't have fun with it, stop using racing soft tires, because no car is meant to fun with that much grip bro