This is true, if you completely ignore Alone at Sea, Gem Hunt, Crack the Whip, Steven Vs. Amethyst, Beta and Earthlings.
Did... I watch a completely different version of these episodes from you? None of those episodes feature looking for Jasper in any sense.
Though if there really was a throw away line "We looked for Jasper, we didn't find her" I'd really like to know.
Since the shows slide towards "Meh, who cares?" is starting to drive me crazy. I swear there is going to be an episode where a Diamond shows up, followed by an episode where the Gems don't even acknowledge she is even here.
And I understand why from a writing standpoint this is happening. Because they want to lighten on the drama since we already had a long stretch of episodes involving extreme paranoia and worry out of the Gems and they don't want to thrust us back into that because of Jasper...
I have no issue with them not wetting their pants because Jasper is on earth. Yet they didn't just drop the tension, they dropped ALL tension and didn't even give the slightest nod to someone who, up to this point, is the greatest enemy the Gems ever fought on the show.
This is Mermaid Melody Season 2 all over again! Except... ok... not AS bad (as Jasper is no where close as threatening as the villain in that and at least Amethyst is training to beat her, partially at least)
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Anyhow I'll explain the concept of Unmotivated Protagonists later... Mermaid Melody Season 2 will always be my primary example of this... but I'll give a basic rundown of what happens.
In Mermaid Melody Season 2 a new villain appears who not only can withstand our main character's full attacks but can also defeat them quite easily. In fact the only reason he doesn't kill them is because his crippling health problems forces him to retreat.
Mermaid Melody Season 1 also featured a powerful opponent who was more then a match for the mermaids, in fact I believe he didn't have crippling health problems.
The difference is in Season 1 the entire plot revolved around the villain and the entire reason the mermaids live on land is a way to not only escape from the villain but also so the villain won't destroy their homes trying to get to them.
In Season 2 while they will acknowledge the villain exists... They do not try to find out who the villain is, where he is, or how to defeat him in anyway... All the stupid plots that mean much less then him are put into the limelight... The mermaids don't even do the bare minimum and team up.
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And no having Jasper appear a lot doesn't count.
In Season 2 of Mermaid Melody every single episode dealt with the main villain (though to admit, I am not aware if they knew the connection between all the villains)