Okay, I'll walk back my post a little here. I don't think Karma as a whole is boring - I actually like the way her primary abilities interact with her passive and her mantra.
What is boring and what is not satisfying about her kit is that shield timing is not meaningful enough. Believe it or not, I actually have 90k Mastery on Nami. There was a time where if I got Support, there was about a 90% chance I would play Nami that game. My beef isn't with people that want to buff up their ADC and peel for days. My beef is with Champions that do this without creating interactive gameplay with meaningful decision-making.
Nami and Soraka don't have 100% up-time on their heals. They don't just get to spam their heals off cooldown. In order to efficiently use their heal cooldowns, they have to time their heals with the moment their adc takes a chunk of damage and they need to know how much they heal for and how much HP the adc has missing.
On the other hand, a Lulu with 45% CDR and Rank 5 E has 100% up-time on her shield. As long as she sits there spamming her E, her shield timing will be 100% efficient. Karma and Janna will be no lower than 90% efficient.
By contrast, the very best Soraka and Nami players are probably about 70-90% efficient with their use of heals.