Methinks the crappy sentai footage quality had lots to do with PAL/NTSC video conversion - it's not like they had the original film to work with, and this was before "remastering" was a thing.
I also wondered about the "Zyu2" stuff. It boggled me that between series their megazord cockpit went from a fairly detailed, techy room with seats to a nondescript green counter they all stood behind, that may have stolen from the juice bar. :P The Thunderzord morphing scenes looked pretty silly as well - but Saban at the time wasn't into leveraging the actual sentai stuff besides the suits and the stock footage, I guess.
I watched most of Gokaiger, mostly for the nostalgia factor since I've been watching PR and sentai in chunks for most of the past 25 years (I also watched all of Gobusters, which makes it the first and only Sentai show I've seen end to end). If we get Gokaisilver, it'll be another oddity as the guy who played him was also an immature kid and it showed in his performance.