I hope you see the difference between propaganda and PR for internal, national use to make happy, people like you, and objective, critical knowledge.
Besides this you seems to still not understand, for countries in NATO or former Soviet Union, weight is not important to classify a vehicle, for us Arjun and T-90 are both MBT's - Main Battle Tanks.
The increase in volume is a reason of throwing everything you can inside, without any, deeper look inside the problem.
1) Ammunition storage - There are different methods for safe ammunition storage, I strongly recommend you to look at Object 640, where there is western like safe ammunition storage and tank still weight less than NATO MBT's. Or Ukrainian T-84-120 and T-84 Yatagan, still below 50 tons, despite western style bustle ammunition storage and improved protection.
2) Turret geometry is a well designed solution to a problem of good protection and low weight in tank vs tank warfare. It is however less universal than in case of NATO tanks. However Arjun does not have the same armor placement like NATO tanks, and as such, is more vurnable than T-90 and NATO tanks.
3) You do no understand that modern accurate FCS is not that accurate that you can hit a tin can from 3,500m, this is a typical TV BS.
Then why Leclerc that have relatively good protection, have bustle mounted autoloader that is from sides protected by composite armor, still weights below 60 tons, it is a tank that weights inbetween 50 and 60 tons... magic trick again?
Of course not, this is just how tanks are properly designed per properly made requirements that take in to consideration, all up to day made improvements in tank designing as well as any solutions with perspectives for future.
Let's get back to T-84-120 and T-84 Yatagan, again both tanks were weighting below 50 tons.
Object 640 is even more interesting, I know that Russians were making attempts on idea to design autoloader module behind a turret like a rifle magazine, wich means if ammunition had been depleted completely, tank get back to maintnance units waitning in some safe place, and special maintnance vehicle replace turret autoloader module, which would be quicker than normal loading, interesting concept I must say.
This is DARPA FMBT, it have a low profile unmanned turret with autoloader under it, and crew in their own, isolated compartment. Front armor is 1,300mm thick composite block, and the thing weights only 55 tons per it's creators calculations. I am sure that weight could be further reduced by replacing 140mm gun and it's ammunition with 120mm analogs, reducing the size of unmanned turret and changing it's protection for something lighter.
Why the vehicle is lighter and still better protected? Because internal volume had been downsized to the hull only.
Why should I stop saying truth? To please you? No way. I will not lie so someone can be happy.
Perhaps, or perhaps not. French were first in the west to break up the pattern, and other countries for a long time are working on tanks with 3 crew members, Americans and Germans were even working on tanks with 2 crew members only. The only problem is that all of their projects were cancelled in 1990's because all the sudden their enemy was not existing anymore, so for approx 10 years there was no point to design such monsters... but times are changing, older design starts to be older, in the end next generation will appear, and the catalyst will be new MBT based on platform "Armata" that is in development. And guess what, "Armata" will have exactly the same design scheme as DARPA FMBT on drawing I posted.