Well, the singers who sang during the time music was banned in Iran (I wouldn't call them the saviors of our music as music was banned in Iran for only about 10-18 years) and were worth listening to, were mostly our big stars of the pre-revolution era who'd moved to LA. but that's just natural. As you say when you have a huge population with lots of singers, the top ones come up and get widely known, thus you get more quality. As was the case with the pre-revolution top singers and it is with the current top singers inside Iran. But the new-comers in LA, from the 80's until now, as they say, har ki ba nanash ghahr karde oomade khanandeh shode.
But of course the tastes are different.
As i said, i don't see any progress in Iranian music overall, either outside or inside, and there is no coincidence that the pop music songs of like Ebi, Dariush, Sattar, Googoosh, Haydeh, etc before revolution and up to mid 2000 is still being played everywhere you go.
Music is matter of taste as you said, personally i am not really enjoying the pop music coming out of Iran, despite lots of resources they have access to.
As i said before, last year i had to go to a Shahdmehr concert(who actually used to be Ok when he was in Iran) and it was total disaster, waste of time and money, no instrument was connected, aval ta akharesh lab khooni bod, he got totally drunk and it got to the point that an old man sitting next to us said, baba in ke dare lab mikhone.
The same night some people who attended his concert attacked his Instagram page, ke felan felan shode ma pol nadidm cassette baraye ma play koni, and he had to close the comment section of his Instagram.