Sona's rework became a disaster, they took her niche, what you would pick her for, Her buffing up her team with weak stats but buffing multiples at the same time and ruined it (And if you do the math at the most the Q gave 1 amp tome and 2 Longswords worth of stats (1.1k gold of stats) the W gave a measily 380 gold per person and the E gave less then 250, on a champion which unless built AP would turn into a flash ult bot come mid game/ make the team be 4v5 or at best a 5 v 5 with a far behind mage, and given champions can get similar kinds of free stats (Yas's double crit, Caits headshot damage, Darius passive armour pen, Jhins 4th shot) it was silly to remove them) by making her a weaker Nami with less survivability and no escapes, Seriously Nami has 2 CC where Sona has 1, Nami has a passive which gives movespeed, Sona have an aura which lasts 3 seconds and a "Meh" range, Nami heals better then Sonas heal and shield combined and Sonas Q ONE bonus damage on his loses to Namis 3 on her E with some powerful poke on her W to boot
The thing is making the Utility scale wasn't a bad idea at the time, though hitting their damage was a mistake (Remember Janna Mid? that wasn't a troll once upon a time) because when players look at the team comp they want often times they'll find the champions that do the most damage and maybe a few extra things, thus AP mages waltz down from mid, use their utility, because its enough to match a utility supports, and shove out Traditional supports with superior damage which will outlast any traditional support (Except Nami and Bard but they were overbuffed) and CC which matches most of the support roster (Blitz, Thresh, Leonna, Naut are the only supports which have more then 1 hard CC that isn't their ult, meanwhile every other support has at least 1 hard CC which a mage can match + their superior damage)
But at this point Utility scaling supports was a mistake as was the mistake of hitting their damage, as you said the Support champions are the ONLY champions which are not allowed to go to any other lane now (Pre-rework Soraka mid was a big problem though I'll admit) meanwhile, Brand, Zyra, Annie, Malz, 4 mid lane mages which even had reworks of various amounts in the mage update go bot lane, Hell they even said "Fuck it" and rebranded (heh) Brand and Zyra to have their primary role as support, Meanwhile, Mid Janna? Nerf! Top lane Lulu? Nerf!
The best idea at this point would be to turn all Traditional supports into Utility mages/tanks/brusiers, allow them to go to other lanes solo, I mean if other lanes can bring their champs down bot and do well then supports should be able to as well