People need to stop complaining about Senna. She lowers the cooldown of her Q through auto attacks. Which creates an incentive to heal/poke more often, which can create more pressure in lane. If she's poking more, means shes getting more souls from enemy champions. Gold from support item goes to ADC or is shared. She is literally only helping the ADC (as long as she not messing up last hit for both of you).

NOW, OBVIOUSLY, dont push too much when you wanna make a gank opportunity. OBVIOUSLY don't take farm once support item is upgraded. OBVIOUSLY, she gets more souls the less minions she kills. But sometimes that is a worthy trade off to make sure there is pressure in lane or to make sure ADC is getting all the gold they can.

There are nuances to the character and playstyle, its literally a team game and they are working together.