Growing up is tough: usually, age brings with it responsibility and, when you’re a punchy little enthusiast plaything like the 2020 Mazda MX-5 Miata, “sensible” is the bogeyman. While that purity of purpose keeps long-time Miata fans happy, though, the pool of potential owners willing to make compromises in everyday driving isn’t getting any bigger. We know Mazda’s little icon …