You definitely could’ve ended the series here
I don't think so honestly. The previous chapter and this one both bring up Mikagami wanting to start a slave dispatch service, with Desmos even nudging Ghee to assist Mikagami in that goal on the business end of that. We haven't even seen that ambition come together yet. Then there's the fact that Mikagami also mentioned in the previous chapter that he wants to find a way to return home, so that he can jump between his home world and the one he's currently in.
That's not even getting into his still ongoing conflict with both Desmos and Zayd. Zayd also appeared recently, having returned back with a vengeance. As for Desmos, Mikagami is still bounded by being her slave. He can't fully realize all of his ambitions without earning his own freedom. He also already has a fight with Desmos scheduled a year from when he and Marl defeated Alexandros and Chris. Frankly, there's a fair amount left to explore in this story that this wouldn't really be a satisfying conclusion imo. The end of the chapter itself seems to imply there's more to come.
I'm still confused how the slavery system works in this universe. Like, our MC seems to be the only guy who is suffering under it. Meanwhile, the other slave girls are kinda casual about it, and their parents aren't even that bothered.
To be fair, we only really see two of their mothers. And one of them does actually take issue with it, clearly having an issue with Mary getting married into slavery. Marl's mother however appears to just give no fucks lol. Mikagami is suffering cuz he wants his freedom while having these ambitions he wants to make come true. But to get that, he needs to go through Desmos to get it. These girls are all his own slaves (and would remain slaves under most conditions even if Mikagami were to be set free), but he treats them like equals rather than like property so they're pretty loyal to him.
Also, Mary, Marl, Alice, and Fine all reacted poorly to being slaves initially. They just made peace with their fates as a result of growing to like & even love Mikagami. Hell, part of the reason Mary joined the coliseum was to find a strong man to hold in marriage. Alice initially wanted to convince Mary & Marl to have them all kill Mikagami and get Zayd to help them flee. Fine tried using the illegal use of the genderswap skill Zayd used on her to appeal to Mikagami to not have sex, while also being a crying mess before they even got into the room. She had less enthusiasm about that coliseum business and was essentially pressured into it.
And in Vivian's case, she's been a slave there for a long time and actually enjoys aspects of that coliseum. Paula doesn't seem to give much fucks about it. Between Vivian's massive losing streaks and Paula's status as a dancer and prostitute at the tavern, they're both quite experienced with engaging in sexual activity. Chris grew to like Mikagami enough after their match. She was already a horny priestess who would write material down in her own book. She clearly grew to be content with things. For example, Mikagami correctly deduced that she (and Fine) did not and could not perceive him as a threat because they don't dislike him. Another example is when marriage was first brought up to Mikagami in the previous chapter, Chris thought to herself how she'd be fine with remaining as his slave. Then there's Dia and Ruby, who treated this shit like a game even after they lost up and until they did the deed. And now they're completely smitten with Mikagami.
All this to say, I don't necessarily disagree with you that the girls aren't exactly displaying urgency to escape their current predicament. I imagine tho that's in large part due to them all liking Mikagami.