I was playing my fighter (originally 2014, updated to 2024) yesterday and I noticed an interesting wording change between the 2014 and 2024 versions of the sentinel feat:

2014

When a creature within 5 feet of you makes an attack against a target other than you (and that target doesn't have this feat), you can use your reaction to make a melee weapon attack against the attacking creature.

2024

Guardian. Immediately after a creature within 5 feet of you takes the Disengage action or hits a target other than you with an attack, you can make an Opportunity Attack against that creature.

So from my understanding, RAW this opportunity attack is more of a payback rather than actually protecting anyone, not allowing me, for example, to push someone away with a pike and set their speed to 0, protecting whoever is beside me. It's still useful for multiattack, but it's kind of a bummer I have to let my ally get hit before I can do smth abt it