Ukranian ability to develop SAM systems is incomparable to their ability to develop tank technology. Granted a serial production will run into quality control issues, corruption, and general efficiency problems. (not unlike those encountered in the Russian defence industry
) But to argue that they can't design an effective upgrade of the T-80 acorss all main systems is ridiculous. They may not be able to build a next generation MBT, or anything similar to the FCS and other similar modular combat system concepts. But they are quite capable to upgrade, and modernize Soviet era technology to something competitive in the modern world.
The main reason Ukraine hasn't won major tank deals is precisely because of the state of their production facilities.