the difference is we knew luffy had to take down kaido
and their fight had at the very least a dedicated 20 chapters to making kaido looking just as impressive as luffy as he got stronger to match him. The contrast in opinion with big mom and kaido is down to the fact the latter fought luffy so he had the panel space to look incredibly impressive. with big mom , oda sort of skipped to the part where she got her ass handed to her. The sort of redemption you are talking about isnt hapenning with these guys and if akainu is any close to aokiji , its not happening either.
That scenario is more applicable to blackbeard. a villain thats actually guaranteed to fight luffy.