Some picks just don't work well.
For the offmeta examples, they all have things that work well(except maybe soraka top, but she has her own benefits). They have UNCONDITIONAL things which suit their lane(or jgl). Talon doesn't have anything. You won't be using your E against a duo lane until lvl 6. He does have base damages, but it puts him at extreme risk, pre-6. Once again, if you use your W as a poke, it will burn through mana like heck, put you at extreme risk due to a lack of escapes, and, because it is AoE, it will push the waves.
When you're ahead, you want the ADC to become godlike. If you compete with the kills, both of you will be behind what you "should be", if you were the one with basically all the gold(A 1/0/8 Blitz and 7/0/1 ADC is better than a 4/0/4 Talon and the same ADC).
Talon's too situational. If you pick him as a support, you will lose more often than not. If you don't win the lane, you can't build utility. He has no utility. You need kills.
No, if you're a squishy support, you're not going to stand there while Talon EWAAQs you. You or your adc will cc him. Talon has no escape after that(except flash). You can do half the squishies HP, but you will die. If you do that trade, you, and possibly the ADC will die. No. Supports are never as conditional as Talon. Because they have utility. A team can always use utility, or tankiness. Teams don't want "squishiness". They don't want "no utility". Keep in mind with Talon, buying support items will also put you further behind. But not buying support items will put your team behind. The only thing Talon has to offer is dmg, and there are various picks that can best him in that,and those picks also have more utility and range then him.
If you want an AD assassin bot, Zed fits the bill much better than Talon. What's your build path for Talon? Which gold item?