I personally like Zoe, but I'll fully agree to there being too many characters, especially ones added later to the game. Other games suffer from not enough characters, so that things either have to progress with the few ones there very slowly, or it ends up being a short game. But with the time loop element to the game, you're spending a lot of time exploring possibilities with the same characters over and over again. You can do a lot more with fewer characters.
I do think they explored the Elizabeth story well enough though. She was basically there as the easy level love interest to keep your attention as things built for the other characters. But I think the devs underestimated the number of milf/mother fans playing the game. When stuff stopped happening as much with Elizabeth to give other characters their time and because her story had run its course in their minds, it left people assuming there'd still be more content in the future and disappointed when there wasn't more. At the same time, we started seeing more new characters to slow down the progress with Ellie, Jessica, and Megan. So maybe that time and effort would have been better spent at focusing on Elizabeth? Many if not all of the new girls have been hot, but for the most part I'm playing this game for its incest element. Adding in a non-incestual love interest this late in the game and making them a way to slow down progress with the incestual ones is a bit frustrating.
I can understand if some people like Zoe, to me she just seems pointless as Ellie could've very well been the "best friend" of Megan and help to push her buttons the same way Zoe is doing. Hell, that would've made much more sense than the current "I'm the new girl in the school, wanna fuck my ass on my first day here? Or meet my mom on my second day?" lore that Ellie has. I agree that some games either suffer from not having enough characters, but then I also think that it is most of the times result of bad and lazy writing. Example can be used with Inceton's other game, the first Summer with Mia where there is (as far as I remember) only three main girls that the main character is banging through the game, and yet the game is able to carry on very well for a good length because of it's writing. As you mentioned, now in this one we have the concept that really would give the main character free hands to try almost everything you could possibly imagine him to do with the girls, yet the game fails to deliver and utilise that concept because there is too many characters and too much happening at the same time so basically there is no way to tie it up together properly. And this same thing is also happening in Summer with Mia 2, where there is too many characters and not enough time for everyone. For some reason for these newest ones they just don't seem to find the balance, and that's really restraining them from hitting the home runs with them.
I do also agree 100% that adding more non-incestual love interests in a heavy incest game from the team called INCEsTON at the middle of the game is kinda interesting twist. Leaving out some of the cast mentioned before, they still would've had the non-incestual love interests in Ellie and Nicole, which would've still given something for everyone, meaning the people who don't care too much about the incest stuff. What I see as a problem here is that it seems like they didn't properly think about what they were doing when adding those extra characters in. Like you said, it took time off from the main girls, and in my opinion really hurt the flow of the story. Not knowing what content the two last episodes will have inside of them, but to me it feels kinda lame that there most likely is going to be only one or two proper solo sex scene with each of the girls. Elizabeth is already covered, Jess had her one-on-one scene in the garage, Megan's first proper solo scene most likely was the latest one in Amy's house (which was once again drunk sex, yay...), Ellie had her own solo scene at the party in that "sex dungeon", Nicole just had her scene in the school, Zoe got railed on the hood of the car, Sophie got hers in the sex swing and Amy got hers too in the party. From the side cast, Chloe got hers as did Ellie's mom also. All that build up for such a small reward in the end, as now all there is left to cover is the main reasons why the day repeats, what will go down in the end of the day and such things before wrapping it up. It really gives the vibes that when adding Amy and Angel in the game, they had different plans for Season 3, but then they just got fed up to the current concept and decided to change things up for Season 3, as why the whole thing now feels off-paced and weird when they are suddenly turning the heat up to maximum and then just shutting it down completely.