I actually really quite like this game. It's simple, but does what it says it does. However, I do have a lot of critique, so read what I have to say with that in mind, instead of thinking that I'm complaining, because I'd really like to see where this goes. I'm trying to list these in the order of importance.
So firstly, some UI changes. The settings button is way too big, and way too close to the shop for what it does. I found myself accidentally clicking it, so I would really recommend moving it to the corner, and making it an universal "gear symbol" instead to also make it smaller.
The settings themselves also lack a lot of things that a game like this needs. First of all, a windowed mode. This is the sort of game you want to move to the background, or another monitor, but currently that is impossible. Secondly, there's no clear way to exit the settings menu, so consider adding an X to the corner. Also, the "reset save" button is way too big too. Make it smaller and hide it to make it harder to accidentally press. Lastly, one optional thing is to have the currency be in scientific notation as a toggle, but currently it's not needed since you only go up to octillion or so.
As for some QOL changes, the zooming thing is a little weird, as someone else pointed out as well. I'd much rather have a dynamic experience with the scroll wheel, or if you stick with this way of zooming, make it easier to zoom out. The current method of pressing the arrow button on the corner is way too inconvenient. I would bind this to a button like the right mouse button, since it's currently unused. The same button could be used for selling employees too, for example. Just try to have the player have more control over the game.
Speaking of control, I'd like to see more cosmetic changes. I'm only asking for something like the option to change the wallpaper, some rugs, and overall making the "brothel" seem like yours. The location for this cosmetic shop could be where the current settings location is, for instance. Something else you could find in this shop could be a sign on the house you can rename, time of day changes, or any other miscellanious thing like a font colour change. Basically a platform for personalising your game, one that you can easily expand in the future.
As for the upgrade system, it's intuitive and easy to understand, but it's a little repetitive since all new employees follow the same algorithm and overall pattern. What I suggest, and this is right out of cookie clicker, is custom names for these upgrades, with descriptions to match. That way you're also looking forward to the upgrades, and not just the "employees". Additionally, try to incentivise buying more employees of the same type by locking the upgrades behind them. There's no real incentive to get 20+ of the employees, since you get all the upgrades as soon as you unlock it. As for what I mean by the custom names, here's a few examples:
Mirror model's 2x upgrade could be called "shinier mirror", where the 10x upgrade could be "perfect reflection"
Dildo lover's 2x upgrade could be "dildo upgrade" (to reflect the change) and the 10x upgrade "more durable lube", rspectively.
I understand why this is not something you've done, but I would really like attention paid here, as well. It really does add a lot, and a certain level of personality. I also would like to see some more general upgrades, some that don't just affect the employees. Maybe something like a +5% increase on all profits, Amy appearing more and giving more, or something dynamic like getting +1% more profit on employee X for every 10 instances of employee Y. Which again, incentivises getting more employees and not just sticking to the 20 or so. Really do think about this, since this again would add a lot, and you have unlimited possibilities.
Now some smaller stuff, bugs maybe. Firstly, some of the white employees' faces are brown. I understand it could be a shading issue, or something else. Either way, it doesn't look as good as it could. This mostly affects the twerqueen and the mirror model (and strap-on by extension), but it is noticeable. Secondly, I would really like it if you couldn't prematurely stop the Amy minigame by misclicking on the collect button before the timer runs out. In fact, it shouldn't even pop up before that. Unless of course this is intentional to make it harder. Also, I would like some clarification in-game on what that minigame does. I have questions like "does clicking certain body parts matter for profit" and "Who even is this". It's only by Necrilem's comment that am I able to call her that. And just one more thing; The roof of the brothel is too wide, it should stop at the tip of the triangle. Instead, it protrudes unnecessarily. Simple fix.
But other than that, you've got a really solid game going on. There's probably something else I could've mentioned too since I do have experience with idle games, but I couldn't fit it all here. Contact me on Discord (wibiz9000) if you want more help, but I think that you'll have your hands full with these considerations. That said, most of these are suggestions, but there are some things in there that the game could really do with. However, that's for you to decide. And just like I said, try to take what I said as critique, because I still do want to see this game advance.