The first ship of a class takes longer to build than subsequent ships of the same class. The first Nimitz carrier required 7 years from the time it was laid down to the time it entered service. But the vast majority of Nimitz carriers that followed required only about 5 years each.
Right now, the Type 003 is taking very long because it's the first ship of its class. Furthermore, it switched from Steam to EMALS catapult after construction had already begun. From what I understand, they had to pause work for several months while they sorted things out. And there was also COVID to deal with.
The first Type 004 carrier will probably face similar complications because it's introducing nuclear power. I do not doubt the first Type 004 will take 6-8 years for construction and trials. But subsequent ships of that class should take much faster. There's no reason to believe they can't match the pace of construction for the Nimitz.
Right now, the Type 003 is taking very long because it's the first ship of its class. Furthermore, it switched from Steam to EMALS catapult after construction had already begun. From what I understand, they had to pause work for several months while they sorted things out. And there was also COVID to deal with.
The first Type 004 carrier will probably face similar complications because it's introducing nuclear power. I do not doubt the first Type 004 will take 6-8 years for construction and trials. But subsequent ships of that class should take much faster. There's no reason to believe they can't match the pace of construction for the Nimitz.