Sound like that The Walking Dead guy!
The Walking Dead could probably outlived Kirkman if people are still invested in zombies 50 years from now. lol
I'm not complaining though, I love this manga!
Never watched the anime though.
Long live Shin Chan.
Shin Chan forever, bro!
The difference between Gintama and animated sitcoms like the Simpsons or King of the Hill is that it actually tries to have an overarching plot. If we were just talking about something fully episodic like that, I wouldn't have anything to complain about because I'd understand what kind of show it is. The problem is we get mixed messages on whether or not we're supposed to take it seriously. There's some very well-defined world building going on in places, which is either ignored shortly after it happens or is an outright troll as was the case with the Elizabeth arc.
With this recent arc and many old ones, it's clear something very big is going on behind the scenes, but if it were to follow the path of the rest of the series, it will just stay in the shadows for possibly hundreds of episodes. It's the same shit that happened to Inuyasha.
In the case of One Piece, there's a very real and well-done sense of progression. You talk as if the crew not being fully assembled (and it still likely isn't) means we're still in the introduction, but we aren't. There has been growth, escalation, and a clear sense of knowing the beginning of the story is a distant memory in-universe. Getting new crewmates is secondary to the journey to Raftel. If people join along the way, that's cool, but it isn't what's on Luffy's mind right now. Gintama on the other hand feels as if it could have just started with the developments that have stuck. Maybe something like 4 or 5 volumes in.
It's just hard for me to get invested in the plot anymore when keeping that all in mind, and the jokes are starting to wear thin as well.
Before
The Simpsons got all stupid, it had plot threads as well. The one that comes to mind is Bleeding Gums Murphy and his relationship with Lisa.
King of the Hill had Khan, who went from Asian stereotype to becoming an integral member of the group later on.
As for Gintama, this was a show that basically shat on the whole idea of endings by writing an ending as a gag episode. You don't like our Evangelion-esque ending? Well, here's the obvious ending that everyone can see a mile coming - Takasugi and Gintoki fighting each other to the death. It's an acknowledgement of how banal the plot would be if it became the heart of the show because, by genre convention, that's the only ending they're basically allowed to have.
Perhaps there can be a feeling of mixed messages - certainly after Benizakura you're expecting some big showdown, because that's what these things (shounen or American funny books) typically lead to - but I feel like they've since addressed what Sorachi thinks about the idea of this confrontation several times already.
It's funny, because I think a lot of the "serious" arcs serve as both a change from the episodic comedy as well as being somewhat parodic pieces themselves. Given that so many of these arcs start off the same way - some gag premise draws Gintoki or the rest of the team into some trollish situation before shit suddenly gets real and people are bleeding and spouting one liners at each other - I feel like there's this little wink and nudge directed to the audience every time one of these arcs happens.
But I think that's part of the social contract that I've made with the series. What is it, in my heteronormative upbringing, that makes male-centered heroic bloodshed tropes so appealing to me? Each and every one of these arcs are formulaic to the point of banality, yet as this Courtesan arc has shown, there is still some raw excitement derived from watching Gintoki get torn down, only to stand up as a result of the bonds of friendship and manliness, and save the day. It both reifies the fetishization of the male hero that we see in all of this kind of media and across all cultures, but it's perfectly self-aware enough that it knows its using and reusing these tropes in order to manipulate the audience.
I've never read
Deadpool or really know anything about the character, but I get the impression - based off of American funny book podcasts - that he exists in the Marvel universe in much the same way that Gintoki exists in this greater... well, "Jump" universe.
I joke on IRC about the fact that no one can seem to explain the "One Piece" and why it's so valuable... and perhaps it's because it's meant to be a Macguffin and the point isn't finding the One Piece but the bonds of friendship and Nakamaism that Luffy makes with his crew and the people he meets/saves along the way. And given its longevity and popularity, it's clear that the story works on a very fundamental level - the same way that Batman and Superman have lasted for decades telling and retelling the same thematic stories over and over again.
I think
Gintama is in on that formula too, but it is using that formula for completely different purposes. In a way, it's why I think the ending of the Courtesan arc is a bit of a troll, because it again acknowledges this supposed end goal of the series that only serves as the "One Piece" of the
Gintama universe. It's there, and supposedly the characters are meant to head in that direction, but it's not really the point of the series.
You've explained my reasons for liking the show better than I did.

Gintama really is an odd duck. When viewed from afar it has the appearance of a typical shounen. Once you get up close you realize, while there are similarities, it's actually quite different.
Cosmic isn't really wrong. Gintama could easily have a deep overarching plot and that would be awesome. What we have instead is a loose overarching plot. I have no control over the direction Gintama heads so I don't let it sour my enjoyment. The episodic or "capsule" nature of the arcs is one of the reasons I like Gintama so much. I can walk in and out of any episode or arc (in any order) and not feel lost. There is great rewatchability, I can't say the same for other shounen series.
I know it's strange to make this assumption, but I almost feel like
Gintama is written for TV first and then turned into a manga for the purposes of keeping the funny book iteration of the franchise going. There is this manically episodic nature that keeps the show from getting too deep into the serialization hole that a lot of shows like this would easily get trapped in.
Of course, another way to put it would be that
Gintama has a shit load of filler. But at least the filler episodes are still fun to watch. lol
Funny enough, this is probably one of the first times that I've given a lot of thought as to why I like
Gintama as a series beyond the visceral reaction of "HOLY FUCK THAT WAS SO AWESOME" that comes from watching nearly every serious arc of the series.
I can almost - ALMOST - understand people that have kept up with
The Simpsons for over 20 years and still find the show enjoyable. I haven't watched a new episode in maybe over a decade, but I have to assume everyone is in on the joke at this point now, right?
Edit - given my avatar, I suppose I should also just say that my fangirl shipping probably helps contribute to my non-intellectual enjoyment of the show. lol