Thornmail needs to be fixed

Riot, this item no longer counters autoattack champions, it's just an item that you get on malphite/rammus and stack massive armor. On every other champions it sucks so hard and deal so little damage.

let's make a complete description of thornmail balance AND design issue. On this current patch it reflects 15% of the damage taken from a basic attack. Meaning that if you take 500 damage from a crit, you will deal 75 damage to the adc, it also deals of your 25% armor, let's be honest a tank that isn't rammus/malphite will have at best 200 armor so you deal 75+50 damage, and i'm asking you: what the fuck? cause 125 damage on 2000 hp is nothing at all in late game, considering that the adc didn't build which is really impossible right now, because everyone undestood that thornmail is countered by magic resistance. be aware that thornmail isn't countered by lifesteal (since you gain 20 hp or 30 hp back by attack) but lifesteal combined with magic resistance can make he entire item useless compared to

But the problem is that thornmail has no window of power, the passive is always here and if thornmail was good there would be no way to play against it.

What riot needs to do is keeping the current power of thornmail's passive while adding an active to it to counter basic attack. It can be an increased return damage, or make it reducing basic attack damage by 15%.