S300 is very good AA, but in practice modern SEAD with a sizeable number of planes can outrange them and they're not great at protecting themselves. We saw this in India-Pakistan and seeing this again in Iran-USA. You can see more of a stale mate when they aren't getting outranged in Ukraine-Russia.

I am talking about the Chinese clones, not the original (is there a difference ?).

As you mention they did not fare very well in the India-Pakistan conflict.