Except that none of these are low end threats. You would never send a 054A out alone if there was a significant risk of being attacked by stealth aircraft or a saturation missile attack. Hell, you would never even send a 055 out alone if there were a significant risk it could get attacked by stealth aircraft or a saturation missile attack. Those are high end threats demanding high end defenses, such as would be provided by SAGs and CSGs. Low end threats such as submarine attacks, missile/gun boats, and random patrolling enemy corvettes/frigates/CG cutters is what the 054A would be expected to face alone or as a small group of 054As during the few missions it would be relegated to: ASW, convoy escort, and near seas wartime patrol.
Those are threats that can pop up literally everywhere, right to China's shore (which is painfully big and has crazy amounts of vulnerable traffic). Even when you develop protection plans for that coastal traffic, you have to take them into account.
Seas around China are just too large to be tightly controlled, but crossing them with aircraft (even non vlo, at lower altitude) is fast enough. All possible kinds of land features around China to the South are sources of attack, and in case of Taiwan, Philippines and japanese islands are explicitly developed as such.
Indian friendship with China is overstated as well. Vietnam tries to avoid this conflict, but it's last nation China fought with (including at sea) in the first place.
For any more remote and offensive activity, say, convoys to forward bases, or supplies to offensive amphibious operations, everything applies even more.
Seeing India as friendly to China is also an overstatement. Few things unite indian politics, but hostility and suspicion to China is definitely one.
Also, I don't agree that submarine attack as a *low end attack*. Neither with cruise missiles, nor with heavyweight torpedoes(which are the deadliest and most sure weapon in modern naval warfare in the first place).
BTW I don't see any reason it couldn't handle a LRASM or two, not that it would even be exposed to such a threat in the first place. Philippines, Singapore, India, Indonesia, etc. don't have this missile and are not inclined to attack China in the first place.
If you spot them in time - yes, no problem, they aren't that difficult as targets per se(though 054a close range options aren't very good). However, you aren't working with a very aware combatant here, even for normal ASCMs. And LRASMs are especially easy to miss.
For example, USMC F-35 presence is more or less expected on Luzon. And this was published just a couple days ago:

This is just a part of general US TACAIR update; most strike fighter platforms there are getting LRASM or/and JSM capabilities(as well as finally get relevant harpoon integration); there was a
just yesterday. Others already have it.
Finally, about B-21s. N
ot expecting them to attack within 1IC is also optimistic - what are they even for, then...
