I mean, from a security point of view, those related to the government should use something they control. This goes for all countries.

For the population in general though and in special those who don't like the people in charge of the country, WhatsApp is a great tool. I have to worry about WhatsApp and Meta as I'm in the "west", but there's no chance in hell Meta's going to provide data on any user to the Iranian government... it's a good option for Iranians.