So what people think about the stock reckon planes of USF and USF that can be called from enemy base and provide vision before being shot down?
That is specifically the key difference here. AA can bring down planes and thus shorten the time that the planes provide recon(obviously requiring an resource investment but key sentence is ''being able to be countered'').
Flares have no way to be countered other than holding all munition points on the map which is ridiculous in comparison to planes or sight extenders like the SU-85 has. I don't remember how long arty flares last but it is usually enough for artillery to fire with clear vision.
These flare abilities need to be restricted in use or outright replaced with abilities that can be countered, like recon planes or sight extenders. The mods have made decent suggestions, making spec ops doctrine open to changes aswell which is welcome.