I think there is a problem with the rewards SPAA get for shooting down planes compared to what they require to upgrade their mods. At lower BRs, you can use gun SPAA to usually support the team directly and can even kill many vehicles that have lighter armor. Once you hit rank ~7 or so and the missile SPAA start showing up, the only thing an OSA-AKM can do for example is shoot down planes. It can’t take points, it can’t support the team with flanking fire or supporting from the rear; it can only shoot down planes and helicopters. With that in mind…
This is the longest grind in the game overall tied with something like helicopters using PvE to grind. It will take me 3-5x as long to spade this single SPAA as it would to spade any given MBT at rank 8.
I think either the rewards for killing planes/helis should be greatly increased (by at least 2x if not 3-4x) or they should simply half the requirements to spade these higher BR SPAAs that are very narrow in their usage.