Are you saying this because you genuinely think they did a good job, or because now you don't have to worry about playing against "cancerous" old Swain?
New Swain's winrate is currently 46.8%. In Diamond - the highest ELO for which there is data available - it's 43.3% as of today. It's been solidly below 50% since his release, and worse at higher ELO. Indeed there's quite a bit of evidence that Riot listened so much to the cries of "cancer" that they underpowered this new version badly.
I was an old-Swain toplane main, and personally I feel like those who were endlessly complaining about his "cancer" did the lane a real disservice. No doubt it wasn't fun to play against a good Swain player - all the same, that can be said about a lot of toplane champions. Give any good Darius, Riven, Jayce, Gnar, Kled, or Fiora one kill and your lane is lost to the point where you can't really be in it. Give a good Nasus zero kills - but twenty or more minutes in lane to farm his Q - and he can potentially fight the entire team 1v5.
Swain was a counter to a lot of those champions, all except Fiora really. Now he can't even lane versus many of them.
I really think League has too many players who throw tantrums, cry foul and ask to nerf champions simply because they lose games. I have never asked to nerf the snowballing toplane champions that I've lost to - instead, I found a counter to them. But others didn't do me the same grace as I did them - so, now I have to put off ranking once again, and either grind and learn different champions, or wait for Swain to get buffed back to a place where he can at least carry a winrate close to 50%.
Feels bad, bird dad.