Why can't all supports be as relevant as sona instead of lessening sona's impact?
Honestly, supports as an archtype are really really powerful, at least in my opinion.
Like, look at how much damage sona puts out early game, look at the how many bot lanes get 1-shoted by taric or ali level 2 if they're with a partner that can put out damage.
I'm oversimplifying I know, but I think supports pretty much define the conditions of what you can't in laning phase because they're the ones with initiation, the laning phase partner defines what happens if you make a mistake as defined by their lane opponent but you're taking a lot of damage from anyone when you're cc'd for 2 seconds.
Those that don't initiate, instead have other equally broken factors, like sona's heal which when it's leveled becomes strong enough that she'll heal off any trade.
And the other thing is since this archtype tends to bring long-term value that generally doesn't require gold to scale (or simply requires very little) it's very difficult to actually shut supports down.
I dunno, this is a reletively uneducated prospective, but I think that supports could do with some across the board nerfs.