It's the ethnic cleansing, genocide and inhuman oppression of the Uighur's that really gets to me (I've taken this matter somewhat personally). On the one hand, this represents a nigh unforgivable act that can't and shouldn't go unnoticed by Iran or the world-community yet on the other China holds the economic cards for Iran's future financial/economic wealth/growth (supposedly) so it's hard to criticize much less "act" against them because of it. Iran doesn't have anybody else to run to for help in this arena as the Europeans states are cucked beyond belief and will lose all their dignity/integrity before they stand up to Israel and the U.S. Other states around the world like India or East Asian nations won't risk American sanctions just to do business with Iran, so that's also out of the question.
China really is the only one left and, well, China needs Iran to see its BRI (Belt and Road Initiative) completed successfully. So even then, China and Iran would have had such talks for an agreement like the "25-year" accord going on at sometime and place. What we do need to acknowledge though is that China is going to want to spread its wings across the globe as now it has the financial and physical ability to do so and wanted to so for quite some time. We are dealing with shrewd, smart thinking long-term tacticians here who think it decades and centuries.
I won't even begin to act like I know what Iran-China relations actually entail and just how much either-side has influence on the other but some of the trends I've seen over the years are indeed concerning. But I have to be hopeful that such relations will be beneficial to Iran.