Disappointing then. Latest Russian APFSDS for 2A82 is said to be capable of penetrating 900mm at 2000m, with American APSFDS being said to penetrate 1000mm+ at 2000m. Other estimates for 3BM69 can also penetrate 1000mm+. It looks like we are far behind in this area, 680mm penetration is early 1980s tech at best...
The Type 99A actually aren't all that impressive at all compared to the latest and greatest western and Russian tanks. How can it be expected to? It's based off the second Type 99 which itself isn't really world leading even in the late 2000s. The T-14 isn't exactly in service and with numbers at the moment but 2A82 and higher calibre versions are all going to be FAR superior to anything in service around the world. The best gun in significant service numbers (so no T-14 ones) is probably the L55 used by the latest Leopard 2s and the K-2. The best round, the M829A4 and the 3BM69.
The Russians have created the next generation of MBTs even though they haven't started fielding them in numbers. The Americans want their best APFSDS round to penetrate the frontal armour of all Chinese and Russian tanks in service. The PLA doesn't have the funding to have developed and fielded its next gen MBT like the Russians, it also doesn't have the funding to change the Type 99 into a design that allows for long penetration rods and one piece ammo to develop something that reaches or exceeds the M829A3/A4 using the current ZPT98 125mm.
Type 96/99 series should be plenty enough to punch through every Japanese and Taiwanese tank in service since the Type 10's armour is genuinely underwhelming to say the least and the Type 90's from another era. Fools will believe the heavier Type 90 is better armoured. It's barely superior to the Type 10's lazy and generous use of high tensile strength steels. Surprisingly poor effort from the Japanese but good mobility and firepower though. Not that Japanese tanks are likely to get deployed in such a way they're facing PLA tanks. 96/99 gun and rounds are also probably good enough to penetrate most Russian 40-50 tonners too and this includes just about all of India's main tank force. Definitely good enough to go through every side armour on the planet. The Arjun is a mystery at over 60 tonnes but who cares honestly. Are they going to air drop them past the Himalayas? lol HJ missiles supplied to Pakistan will make 100 Arjuns light work within a hour if they really decide to send those crawling elephants into the desert. The Americans won't be dropping Abrams and the Koreans will at most be fighting the North with their impressive K-2s before their 2-3 hundred stock will see Chinese border IF such a crisis ever happens. Now it becomes more obvious why drones and WZ-10s are probably prioritised over MBTs. PLA MBTs are there to hold an already captured territory or storm through with overwhelming air and artillery support, facing at most a random IFV and foot soldiers firing ATGMs if they get a chance to slip through. That's where modular armour, FY-3/4 ERA, and GL-5 APS come into the picture. They aren't going to be facing vastly superior MBTs in equal number face-offs, at most if they face other MBTs, PLA will be able to totally outflank and outnumber them, punching through side armour like hot knife through butter.
Type 15 project was a GREAT opportunity to explore a newer design philosophy, using the K-2/Leclerc like autoloader and ammo storage layout. It's a low risk way to work towards exploring different paths which are used as learning steps in designing a next gen MBT. It's also something the PLA has a gap in - high altitude, light, superior mobility to any MBT, incredible hp/t, low tonnage surface/bridge crossing, flexible, urban competent with narrow and compact size aided by APS against the main urban threat. Honestly PLA's doctrine and situation makes the Type 96A/B the real "most valuable player" overall like an AK-47 of combat effectiveness for the PLA's particular needs and way of war. Spending time and money developing super tanks like the T-14/ K-2 etc would have been a huge blunder when the talent and money should be focused on 21st century weapons. I wouldn't say Type 99A's firepower is 1980s, maybe early 2000s lead level overall but it's better to have vast and varied combat drones, than world leading MBT firepower.