The insecurity that the Loki’s character is rising is kinda weird ngl
I mean I do not think that Loki is stronger than Kaido BUT One Piece is a shonen nekketsu and in this genre of litterature the new threat (and I do not think that Loki is one) is stronger than the last threat.
So at one point Luffy will fight someone stronger than Kaido because, yes, Kaido will be powercrept. Which is also why, the latter a character show his strength the stronger he is.