The best swipe-typing I've ever used was on my Windows phone of five or six years ago. GBoard is so-so, Apple's is terrible, and--what's really odd to my mind--SwiftKey is pretty bad, too, despite belonging to the same company behind Windows Phone.
SwiftKey keeps telling me how many presses I'm saving by using SwiftKey. Does that count all the delete, retry, delete, retry, delete, give up, type manually-cycles I'm doing? It's slightly better than having to type by hand but it still feels like having both hands tied behind my back and typing with my nose. I can't even get through one short sentence without deleting and retrying several times on some words...