As simple as that
It would be proved only if Sorachi would had wrote a novel about Gintoki's ventures instead of drawing crappy characters with long texted jokes and cliché drama with forced conclusions to make mc's look absurdity awesome.
First of all, there's a Gintama novel. Second, long-text jokes and cliché drama seems like a simple grab to bitch about something. Yes, there are some jokes that require reading, but that might be about 5% of all the comedy in the 700-chapter manga.
Cliché drama? You mean drama you've kind of seen before? As in the drama that literally
every other media product ever does? Yeah, Gintama has some of that. I can't deny that. Seems you couldn't make a connection with the characters or the material. For a shounen, Gintama is one of the best regarding it's serious drama/action arcs,
in my opinion. Regarding it's comedy, it's hit or miss. It's Japanese comedy for a Japanese target audience, that either works for us non-Japs or it doesn't. I don't laugh every chapter/episode either, But overall it's one of the few comedy/gag anime/manga that I actually enjoy for it's comedy.