In Karaj, a city near Tehran, one resident said he had not heard much about Mojtaba Khamenei before his appointment.
“Now it will become clear whether Trump has done a deal with them or not. They need to target him,” the man in his 20s said.
Another man said he believed “this means that nothing is going to change”.
“It’s the same path, perhaps even worse,” he added. “I don’t think that he will last.”
Earlier this week, US President Donald Trump said he had wanted to play a role in the selection of Iran’s new supreme leader, and that Mojtaba Khamenei was “unacceptable”.
And just hours before the appointment was announced, Trump said that, without his approval, whoever took over was “not going to last long”.
Israel also issued a warning before Ali Khamenei’s son was confirmed as the new leader, saying it would “continue to pursue every successor”.