If it is a re-manufactured existing fighter, it means nothing.
If Iran can produce new F-5's from scratch, it is a huge step forward for Iran.
Consider China, it has taken them decades, but they have finally transitioned from reverse engineering to designing their own aircraft.
You can count the number of countries capable of producing supersonic fighters on your fingers. Despite the age of the technology and the fact that they copied it from, this is a real achievement...
But if they just performed an overhaul on existing airframes, they haven't really achieved much more than they have already been doing for years.