I think the biggest contribution China made are threefold.
Firstly, China supplied weapons such as the aforementioned J7s as well as heavy artillery.
Secondly, China provided advisors, who brought a paradigm shift in thinking of how to deal with the Tigers, in strategy more so than tactics.
Lastly, China provided diplomatic cover and a free hand for Sri Lanker to do what must be done to end the war.
With no disrespect, but I think the West, with the exception of maybe America, simply lack the stomach to win a war, or even an understanding of the real nature of war, especially a dirty, messy counter insurgency war. Such wars are no gentlemanly dual between rival armies out where there are no civilians to get caught in the middle.
When the enemy actively hide amongst the innocent, zero collateral damage is simply not possible, and too much focus on no civilian casualties will mean you loose sight of the actual strategic objectives that you need to achieve to actually have a hope of winning the war.
The other western obsession that gets in the way of victory is their obsession with minimal casualties of their own. If you want to win a counter insurgency war, you need boots on the ground holding the ground and denying it to the enemy. When you have boots on the ground, a certain level of losses are unavoidable, but that level is simply unacceptable to most western nations. So Their soldiers hole up in forts out in the middle of nowhere, where it is safe and easy to defend, but that necessitate the forts being separate from the local civilian population, so those troops cannot keep an eye the locals and make sure they are not giving help and shelter to the rebels, but that in effect defeats the whole purpose of having those troops there in the first place.
The bleeding hearts in the west love to chastise Sri Lanker for the way it ended the civil war and the civilian casualties that ensued. To some extent they are right, the massed rapes and massacres are indefensible and a blight on the victory of Sri Lanker, as was the gulag like conditions the Tamil civilians were subjected to. But the government forces' decision to not agree to a humanitarian ceasefire to allow civilians to get out, to instead press their advantage relentlessly and not give the rebels any time to recover and regroup or escape, that was a sound decision and no apologies should be made for it.
Yes, innocents undoubtably suffered and died as a result of that decision, but that was a necessary evil to end the civil war quickly and decisively. The few hundreds or thousands of civilians who were trapped and died as a result is a small price to pay next to the prospect of another three decades of grinding civil war and tens of thousands more dead.
When Sri Lanker was under the thumb of the west and forced to fight according to the sanitised, romanticised ideal of war the west now hold, it was little wonder they did not get much done when the west complained and pressured the government whenever any civilians got caught in the crossfire and had their broken, bloody bodies photographed and splashed all over the news.
The west may think themselves enlightened, and perhaps they are, but enlightenment does not change the brutal, harsh realities of war, especially if you are fighting an enemy who still play by the rules of the dark ages. To defeat such a foe, you need to get down off your ivory tower and get your hands dirty. The really difficult part is not getting your hands dirty, that is easy, frighteningly so, the really hard thing is to keep hold of your faith and ideals even as you are forced to do horrible things, so that you only do what must be done and no more, that you may win the war without turning into the very monsters you oppose.
