A ship as heavy as this vessel it weighs as much as a UGI Dreadnought which is 3 times longer and 9 times bigger total. Making this vessel impossible to go into atmosphere. Although dreadnoughts can go into atmosphere the Extant-class does have a super structure to allow it to be able to stay in the proper shape but by going into atmosphere will cause the structure to fail and be destroyed. These ships have to be built in orbit of the planet or else the ship will never leave the ground. Another thing about these vessels is that they are so heavily armed and armored. They cannot be easily killed due to Derexium plate ablative armor which is a sheet of metal that was composed of Duranium, Titanium, Neutronium, and Carbide in a sheet of metal that is 19 meters thick and was compressed till it was 3.5 meters thick creating Derexium, a metal that Starfleet cannot build at moment.
Due to its immense cost it was more expensive to build these vessels than to build a Leviathan, it actually cost the UGI 1.5 Leviathans to build this ship. Its shielding technology is 15 years more advanced than UGI's shielding technology. With this being said it has 2 10 gJ shielding generators that sounds like not very much shielding but a single 10 gJ shielding generator produces a shield that is 500 gJ shielding it just means that it requires 10 gJ of antimatter energy to produce a 500 gJ shield. This ship is easily the most advanced and most expensive vessel ever constructed proportionately.
During construction of the U.S.S. Judgment they wanted to make sure that the ship was perfectly built and when in construction the UGI dispatched the 12th Fleet to protect the only prototype. When it was finished building the UGI saw its potential but couldn't justify the immense cost and the U.S.S. Judgment after 6 years of construction was the first and last Extant-class every built.
The best thing about the Extant-class was the fact that Photon Torpedoes literally bounce off the ship, causing them to either detonate away from the ship. As well as they can be equipped with several subsystems as they have 5 slots for a sub system to be installed.
The most common subsystem to be installed on any UGI ship is communication jamming that prevents the enemy from communicating with their allies essentially dividing and conquering. While their is sensor/lock jammer that prevents the enemy from using their systems as well getting a lock-on with their missiles and ships cannot fire a missile without a lock on. When the U.S.S. Judgment disappeared from their reality the UGI was distrought that nearly 500 trillion credits and 6 years of work was just gone. The UGI was forced to hide that it disappeared and created a second Extant-class also known as the U.S.S. Judgment but this wasn't a pure Extant as it was just a Harridan-class that had Derexium armor plating which is the main reason it was so expensive.
Most of the technology on the U.S.S. Judgment is highly classified as UGI has linked it to Division 11 technology but believe it be technology that was literally from the future, using it on the Judgment they wanted to build a vessel that was perfect in every sense. And to make things more strange was that they built it to be staffed and crewed by Taiidans only as Division 11 is entirely Taiidan. The total cost of the U.S.S. Judgment was 750 trillion credits which in starfleet's currency a UGI credit is 4 times more valuable as their economy was stronger and better due to being around 250 years longer than Starfleet. With a highly sophisticated economy the ship's price was negilable at first but then again was proven to be too costly of a project.