One other point that bears mentioning is that foreign weapons - particularly when rushed to an emerging warzone and placed in the hands of local combatants - run a risk of being misused, which may hamper their effectiveness.
I recall Konrad Muzyka (the Rochan guy), who - following one of his tours of the Ukrainian frontlines - remarked that the lower efficiency of HIMARS in this conflict compared to what was seen e.g. during the Gulf War is not so much due to Russian countermeasures as to the fact that the Ukrainian operators are not as proficient at operating the system as Americans.
The same may also be true for Iranians, should they receive new weapons systems from e.g. Russia or China. The world's fastest car will not win any races if it isn't driven by an accomplished racing driver - and likewise, advanced weapons need to be used in accordance with a well thought out doctrine, which directs when, where and how they are to be employed. Failure to do so may lead one to falsely conclude that there's something wrong with the weapons themselves.