Panna cotta occupies its own special spot in the dessert world, as a custard that that’s not really a custard. Oh sure, it may look a bit like a custard, it may feel a bit like a custard in the mouth, but in the end it’s what we moderns call, rather unceremoniously, a “gelatin dessert”.
True custards are thickened with eggs. That’s what makes them yellow and gives them their eggy flavor. Panna cotta, being thickened with colorless, flavorless gelatin, not only has a different look and feel to it, it has a purity of flavor that “real” custards simply can’t match.