Wait is if thought that TRO golden century was still on the drawing board? Also with the pounding that the jag navy took why wouldn’t they try to save the mongoose for a rainy day?
Firstly, the Jags have never been a strong industrial power, relying on combat to get the resources they need. They may not have the facilities to repair that ship, and they certainly don't have any friends willing to help them do it.
The second reason is psychological, and far more important. Clan Smoke Jaguar is the ultimate distillation of the Might Makes Right philosophy of the Clans, and the Mongooses were defeated. Therefore they and everything they made is Wrong. Individual warriors might be more pragmatic, but there's no way the Clan's leadership would allow the
Mongoose to be put back into service, same way they refused to use any of the Mongoose bloodlines they now owned.
It would still be their property though, so they'd fight bitterly to makesure nobody else used the ship either.