Well I've played the new update for a couple of days (as best I could, had to reload the game very often to avoid the event/fullscreen lockup bugs), and here are my thoughts on the addition of the charts:
Very neat, and provides a nice layer of immersion! The trending genres plus your tweaks to the demographics with a "soft cap", whatever those are, have helped make my game more engaging/challenging in a fun way. Before I'd be plowing through the game with 500k+ singles after the first election: now I'm still having trouble selling all copies of my singles at single 12, and that's with ~20k sales. I'm much more invested now, now that the game seems to be better paced, and I'm enjoying watching my group climb the chart little by little. I'm also changing strategies between each single in order to increase sales, which is engaging.
If I were to nitpick: the chart could be more dynamic, both in groups and song titles. I think the pool the game uses to generate song names could be widened a bit, cuz I get a LOT of iterations of "She/He Knows/Thinks..." "...Her/His Love", etc. It's not super noticeable when used for the player's single name generation (since it's one title and I think a player would rarely use it), but when it's generating 29 titles at once every month, it gets very repetitive (There was a point where I got a string of around 10 songs all being in the "He Knows I Love the ___" format for the same month.)
I also think the ranking could be more dynamic: I like how the sales can fluctuate somewhat (ie the top group generally sells 1million but can dip below this every so often), it feels like the 28 groups on the chart excluding you and your rival keep their positions, with only the sales total changing in step with every other group (To keep the aforementioned ranking). I notice slight changes, but it's always with a +/-1 deviation. Top 10 always does 100k+, etc... While the chart feels real, the groups/songs that populate it do not, and could use some work. Something as simple as new groups entering the charts over time, old groups exiting and returning, rising/falling... I also feel like generating more groups would help? Having 30 positions still, but maybe not every group releasing monthly could add variety.
I believe "Groupe idol rival : [blank]" is the rival group devs hinted at? (That is how it shows up on screen, btw, mine is called "Groupe idol rival : FairyGirl's"). I'm guessing more will be added to them, but I'm not sure how I feel about them ALWAYS selling just a bit more than you, rather than being subject to the same trends as you are (As in, I kept selling more with each single, and they were always ahead: THEN I sold a little less with my next single and then they ALSO sold a little less.).
And for a hope, I'd love to possibly see the subgenres incorporated somehow, like in the kickstarter video! Would help to personalize singles even more.