Everyone in OP gets stronger and stronger in weeks with no reason. At least Sanji's growth makes sense
Usopp - > learned CoO in a extreme situation and has to improve it by himself
Chopper - > Improved his Monster Point by his own
Franky - > no power up, just has gone all out first time since the time skip
Robin -> Has gone all out the first time since the time skip and had to learn the fishmen- karate technique
Zoro - > He copied Kinemon's technique by just taking a look at it , but still had to learn it by himself, Enma was granted to him, but still had to learn to control it, same goes to advanced CoC
Luffy -> Was bullied for 11 hours by Katakuri in order to get a grasp on future sight, Hyogoro was giving hime some instructions, but he still had to figure out how to learn advanced CoA and CoC and work on mastering it by himself
Law/Kid - > Had to figure out Awakening on their own, which they haven't mastered yet at all- stamina waste is still something they have to figure out to be reduced on their own
Sanji -> His brother gifted him a Raid Suit that his daddy crafted for him, that requires zero mastery in order to be able to use it to it's full extend, also awakened his exoskeleton on a random and convient occaision, which also was another of Judge's doings.
Only one left who was granted a cheap power is Nami....She is piss weak physically, has no access to haki and more importantly rooting for science- so it suits her thematically as well, hence it's understandable and reasonable.