You can fight planes with a lot more than missiles, and missiles are not the most effective. Gauss and Rivet gun do some serious damage on planes from long range, and if you wanna get close you can bring ELC.
The countermeasure is not mandatory either, since you can break LoS from missiles, or shoot them down. Plus it's very cheap, so what about bringing the countermeasure if missiles are a problem for you? it's literally designed for that, and it's cheaper than a single missile.
Ofc it's about timing, but if you're bad at timing, nothing stops you from bringing more than one Countermeasure.
If a good hit disables or kills you, build better