Patch 11.16 in League of Legends brought some major changes to the kit of Sona and Karma. The two enchanter support champions are rarely seen on the Summoner’s Rift, and the changes are intended to improve their state of balance.
Why are enchanter supports getting reworked?

Support is one of the least popular roles in League of Legends. If not played efficiently, the role can be underwhelming and less impactful. However, supports play an integral part in the game. Support’s job is to help their ADC develop into a powerhouse in the game’s later stages, which can be tough without adequate knowledge of the game.
Normally players prefer champions like Brand, Nautilus, or Pyke in the support role since they have great engage abilities and are less reliant on their teams. But with the introduction of these new changes to Karma and Sona, the meta is likely to shift.
Most support players enchanter supports like Karma, Janna, or Nami because they are considered boring and weak. Since these champions are too team reliant, they hardly see any play in the low-elos. While these enchanter supports are more common in high-elos games, most players are unaware of their potential, which Riot Games hopes to improve.
The beginning of a new era

Riot Games is attempting to move past the meta of heavy-engage carry-supports by adjusting enchanter supports like Karma and Sona.
The new changes open the door to selecting various enchanter supports and altering them in such a way that increases their power level when played as a support. Karma may have been a strong solo laner, but new changes have turned her into a full support champion.
If another enchanter support Nami was to receive changes, her damage will probably get nerfed, which will likely get compensated by increased healing potential.
In conclusion, Riot Games intends to reduce the individual strength of enchanter supports by taking away some of their damage but increasing their healing and shielding capabilities.