Saying they went away is a... interesting way to frame it....
You mean getting crushed lol?
Oda doesn't really intend on them being very strong, not like Teach/Loki, who have actually been stronger than Luffy for most of the manga, and most likely currently are. They don't have characters they're going to surpass in the same way either, which is why Oda didn't let them "1v1" BM.
Teach, sure. But I’m tbh hesitant on jumping this much on the Loki bandwagon. Kid and Law are legacy characters who’ve kept up with Luffy for nearly half the manga now. Loki is a relatively new character. You read WCI and the guy tbh sounds like a fodder.
I think similar to how Big Mom and Kaido, in the grand scheme of things, were just entry level yonkos, Loki is probably an entry level “god tier”.
Our first glimpse into the strength of the void century legends. But consider that if Loki gets domi reversi’d, which he likely will, Luffy will surpass him this arc.
I think Law is directly tied to Imu, as Imu is immortal. Kid on the other hand could tie into the ancient kingdom’s technology, as the main power of his fruit is creating structures out of metal and Oda drew him playing with a robot as a child.