Not bad, we are approaching Western non-DU standards.
Btw, when Arjun was offered for mass production, and T-90 license production was initiated, the best shell available for Arjun was the first one. While the Mk2 says 2010-15, it took longer than that, closer to 2020. The best T-90 Russian ammo the Indian version could fire was the Mango, with up to 470 mm penetration, and an Israeli Mk2 with 520 mm; 0 deg at 2000 m. There's a new shell called Mango 2 which does 550-600 mm with a new penetrator. The new T-90 Mk3 can fire the older Lekalos, which can do 550-600 mm, and the newer Svinets-2, which can do 700+ mm.
So the T-90 has consistently been maintaining firepower superiority over the Arjun. Things should improve for the Arjun after 2030 when more advanced rounds are created for it while the T-90's tech development stagnates in Russia due to autoloader limitations and the two-piece ammo design.
While European tanks are at the same level, the latest American DU rounds can penetrate a meter or more. Russia's Vacuum rounds for Armata, both tungsten and DU, can manage the same. That's why Armata has 1.2 m of armor, meant to manage tank shell developments for the next 20-30 years.