I don't feel the characters were lacking in anyway either. One thing Gokaiger did that alot of other series neglect to do is have the characters shine their personalities through all the time. The cast of Gokaiger was pretty much brimming with it whether you liked it or not. In the way they fought, in their reactions to things or even if they were just doing something in the background, you could tell alot about them just from those little things so they didn't need an entire episode focusing on them for you to get the gist of who they are.
That's all true, and the main reason Gokaiger is one of my favorites. Appealing main characters' is the basis of a good Sentai in my view, and the Gokaigers had undeniable presence and chemistry.
And unlike the stale Go-Busters, the things that happened to them used to affect the characters in a permanent way, with consequences. They all got some sort of personal development or change through the series (some subtle things, like the way Luka treated Ahim in the beginning as a replacement for her lost sister), and Gai was the best sixth in like forever, breaking a recent trend of extra heroes who get neglected some time after their introduction. It was just more obvious with Marvelous and Joe because they had recurring rivals - but then again, most Sentai only give Red a rival.
Those personal reactions you mentioned, even in the backgrounds, were also a great touch that humanized the characters, made them look real. I really don't see much of that in Sentai - heck, while they showed who they were even by those small details, the Go-Busters rarely display their personalities, ever. You could tell a lot of effort was put in the series' direction.
And according to some articles it seems apparently the series wasn't meant to have nearly as many cameos as it ended up having so it seems alot of this stuff was added last minute and if that is all true and this was a rush job it's probably one of the best put together rush jobs ever. To manage to get all these actors back and make these homage episodes and have them not be horrible is kind of amazing. The show just carries itself on the fundamentals of the franchise and just does it in a bigger more over the top scale than usual, that's usually how anniversary things work.
Yeah, that information gave me even more respect for this series. Even with such little time for planning and i imagine a lot of improvising involved, 90% of the time the guests were used to help the story or develop one of the characters in some way. Not to mention it managed to keep a sense of coherence and tightness, which is more than i can say for most Toei series lately - even when pulling episodes like the Timeranger one, managing to tie different series and events together in a very satisfying (and impressive) way.
It's a miracle it didn't end up as another Decade, and i think Naruhisa Arakawa deserves mad props for that.
HA. I'm assuming this means you've never watched any Showa era sentai.
I do agree that, in the 2000's, Toei series had its narrative strongly influenced by anime, and i see why that can put people off....but most showa shows used to have very, VERY simple/flat main characters who would rarely get any sort of development, and honestly, Sentai was almost never about plot. We would have 40-ish episodes of MOTW that barely mattered and 10 to move the plot.
The "slapstickness" was there too, it was just a different time. But it's human nature to be harsher with the new.