That's even worse is that Rulue was essentially *forced* into being an antagonist in PPT, and then once you fought her, she disappears. The really bad part of this is, PPT (and Sonic Mania) really extended the awareness of Puyo and Madou Monogatari. This is going to give a lot of people bad impressions because of the characters.
What really sticks out to me is the fact that Arle, while a decent enough character, is a failure as a JRPG protagonist. I know Madou Monogatari is supposed to not rely on cliches and tropes, which it does very well. Madou RPGs are for the most part a single character RPGs, but put Arle in a "group" setting, like say Madou Saturn and she falls flat on her face. Arle is an adorably cute girl with a yellow pikachu mascot, but thats all she's got going for her. She is introverted, reactive (as in she waits for things to happen and just react to them), she acts exasperated when having to deal with conflict, she treats everyone she comes across like a chore, Rulue is the only person that even wanted to have anything to do with Arle prior to fever (and Rulue had to initiate the friendship), Arle comes off as kind of a hypocrite in Saturn, when she essential gave main character status to Rulue and just simply responds to everything Rulue does with snark (because admittedly none of the Madou characters really help the plot), the way she accuses Rulue in 15th of being a troublemaker makes me want to slap her, because of all the trouble Arle goes through to get back home, you think the closest thing to a best friend would be glad to see her, but no I guess since we have Amitie and Ringo we don't need Arle anymore (oh and as much as I despise Raffina, she is generally concerned with Arle's well being as well as Lidelle's, and Arle aslo likes to lump Rulue together with other people she has negative encounters with).
Arle in general is someone who looks cute with her cuddly pet sidekick, but when she loses him in Yon, she kind of loses her shit on everyone because her only friend is now gone and she has no one, and it shows. It kind of makes the point that Arle treats dealing with people like a chore and is only interested in studying and playing with Carbuncle. Just to further the point to it, Schezo has a lot of the same traits Arle does, with his introverted loner mentality and obsession with getting more powerful. This doesn't make Arle a bad or unlikable character, she simply isn't "Main Character" material. (That said, I think young Arle from Kindergarden is adorable).
Amitie carries much better weight as a main character, because she interacts with everyone in Primp Town so much better. Her characters traits are much more endearing even when she is naive or clumsy, because she acts like a human being instead of a plot device (even though Primp Town is more or less a school setting with the usual archetypes). While we are on that topic, Sig is a good example of making an introverted character likable.