Maybe it has to do with politics... IRGC being the guard of islamic republic ideology while the army is neutral, not ideological. So you can guess who will get more attention.
Whereas the regular military (artesh) defends Iran's borders and maintains internal order, according to the Iranian constitution, the Revolutionary Guard (pasdaran) is intended to protect the country's Islamic system.
Even during the war against Iraq we had nationalists in artesh who literally didn't give a damn about khomeini and his ideology.
This point was true in early days of revolution and still perhaps is partly true. But now, both these forces are "ideologically" on the same level since the old commanders are all retired. In fact there was even the idea of merging the two together as they had done with police and "komiteh". But there are some serious differences between the two which could not be resolved and thus, this merger did not happen:
1) Iranian army uses/strives to use the third generation warfare as its fighting doctrine while GC deals with fourth generation. It is difficult to merge these two together as Iran needs both for the nation's defense.
2) Army is concerned with "secular" defense of the nation, its integrity and all in a nationalistic manner, but GC is more into religious aspect and has developed complicated relationships with groups outside Iran. The wars all around Iran, are nowadays of religious nature, in which army would not have been efficient in managing due to its structural objectives, unlike GC. A Shia fighter in Iraq or Syria can trust a GC commander whose base ideology is religious more than an army commander whose base ideology is nationalistic.
3) The army is large and therefore more inefficient and less mobile. It can bring in tremendous amount of power, but not as quickly and as efficiently as a smaller force.
There are other points too. But the reason why army soldier is not as well equipped, has to do with economy which can only dedicate a small portion of its output to military typically around 5%. So funds in smaller economies like Iran are always short. But there are other reasons as well:
1) After Saddam was defeated in couple of months, submitting to American demands unconditionally in 1990, while Iran had not been able to do so in 8 years, the Iranian commanders knew, there was something terribly wrong with Iranian military. So they started to go for other kinds of power tools while under sanctions in order to sustain Iran's sovereignty, from missile technology to nuclear technology. If F-14 and chieftains could not do it, then other things must be introduced.
2) After the Iraq war of 2003, the Iranian commanders learned that no matter how well equipped the soldiers, the nation will fall within weeks, if a technologically superior state attacked it. So the focus was shifted not on soldiers in army but on air defense and submarines in artesh. This made sense since all sophisticated states attack other nations in this day and age from Sea and Air. Soldiers do not play as much of an important role anymore.
3) The GC by comparison focused on longer range missile tech and asymmetrical near shore surface naval capability.
The kalashnikov is the only submachine gun that has passed the same most extreme tests in the world. so you can conclude why the most elite forces, operating in extreme desert and mountain conditions will choose it over any other untested one. One should know that most special forces of the world pick their weapons based on the missions and the environment where they will operate. I do not think that the Iranian army units lack funds for new weapons but it is what I have just said that determines the weapon choice for a mission...
Yes, it is very reliable due to its simple design, sacrificing accuracy for reliability. An accurate and fancy gun that quits firing while enemy is afew meters away from you, is useless. An ugly and less accurate one that fires tirelessly wins the day.
Good going. Why doesn't Iran participate in exercises with other friendly nations (China, Russia ...) or SCO exercises ? Don't think sanction could restrict that.
Because Iran is exercising (its muscles) in conflicts from the shores of Mediterranean sea to the red sea. Not much time is left for lifting weight with buddies in a gym when you are doing the real job: