Also Riot has been implementing and buffing for years items that negate plays instead of opening opportunities for plays.

By negating a play of your opponent you open up plays for yourself. BKB makes you immune to one subset of damage which allows you to play aggressively. Just because an item is "defensive" in nature doesn't mean it doesn't allow for aggression.

stuff like Ardent Censer, Redemption, Aegis scalling with users health, Stoneplate,

These are all items that are "defensive" in that they either have duality in interaction (redemption affecting both enemies and allies) or singular forms of interaction (shielding/healing/defensive buffs). No matter the interaction they still allow your to make plays and be aggressive because they give you some type of edge.

Even if you believe that X team having Ardents means Y team will be less likely to go for a fight then you have to also believe X team is more likely to go for a fight because they have an advantage.

are all shit that negates all the damage that a poke comp or pick comp might do.

How would redemption, Aegis, or stoneplate help against a poke comp? One is an active that gains most of its benefit from being activated when surrounded by enemies and the other two are long CD items that give an influx of pseudo or real health... neither of which can sustain you from poke.

As for a pick comp if you're actively looking to pick off an enemy with a stoneplate then you're playing that composition wrong. If you're getting picked off and you have an aegis, ardent, or redemption the chances of any of those items saving you is very low.