Why don't Iran implement Chinese's style firewall Block west social media, develop some alternatives.
I know their young population is very naive and vulnerable to western media just by watching some street interviews.
The national internet of Iran, which would resemble China's firewall, has been under discussion and planned for ages, with preliminary steps taken already. However, it has never come to fruition so far, although as you correctly observed, it would massively roll back not just the political propaganda and psy-ops of the enemy, aimed at brainwashing Iranians against their ruling political order, but also and perhaps more importantly, hinder the enemy's cultural soft war, which includes deep social engineering.
These instruments are all tailored to channel the Iranian nation and civilization towards ultimate self-destruction on every level (inciting rebellion against authorities, whitewashing terrorist grouplets, promoting "ethnic" separatism, targeting the family structure by advertising homosexualism and third generation feminism, vilifying marriage and glorifying premarital relations, encouraging conflicts between males and females as well as between children and parents, worsening the dangerous demographic slump by calling on people not to generate offspring but keep dogs instead, etc).
Note that Iran has been the worldwide biggest target of propaganda by NATO regimes, Isra"el", the globalist oligarchy and their regional client states. For instance, if you compare the quantity of posts published by the Persian language service of the BBC on "social media", with the quantity of entries from the Chinese and Russian services of the same BBC, you'll notice that the Persian one is several fold more prolific, despite the fact that Iran's has a smaller population than Russia let alone China. This was verified one or two years ago, when a popular Iranian YouTuber conducted a comparative study to this effect.
Personally, I would see two reasons behind this failure to complete and implement the national internet project:
1) The presence amidst Iran's political system of a pro-western fifth column which is delaying, sabotaging and blocking it with all its power. The Iranian polity is a factional one with multiple political parties and currents competing at elections, but to simplify there are two main political camps: the revolutionary core of the system, embodied by the Supreme Leadership as well as the principlists and Hezbollahis, who are loyal to original ideology of the anti-imperialist 1979 Islamic Revolution led by Imam Khomeini (r.A.a.); and a second camp made of two factions, reformists and moderates.
This latter camp is thoroughly liberal from the ideological viewpoint, and its goal is to operate "regime change" from within à la Gorbachev, in order to do away with about every foundational principle of the Islamic Revolution and revert back to the conditions prevailing under the ousted, western-subservient Pahlavi monarchy (shah regime). In short, to turn Iran into a western client state again, abandon the drive towards technological, industrial and agricultural self-sufficiency and replace the Islamic nature of the political order with western-style liberal secularism.
This makes the Islamic Republic one of the most pluralistic governing systems in the world, a measure of how democratic it really is, because one of two main political camps intends to overthrow the political order and is therefore anti-constitutional. I know of no other country allowing this. However, the system is astutely constructed and was extremely well designed by its founders, so that several institutional checks are in place which prevent the liberals from completely and easily hijacking it.
2) Possibly a balancing act by the revolutionary core of the Islamic Republic, which may calculate that keeping open Iranian citizens' access to these hostile foreign media might act as a compromise solution to discourage the liberal camp from radicalizing itself and causing instability.