So I get that you are venting and I agree with some points there, but I just want to ease some of the bias here.
You get 120 gems per week and a 3 item gacha ticket per day, yeah there is a paywall, but its not that bad as a free player, just gotta get over that and the fact that you are playing a free game with money options to speed up the process, and that you have to grind alot more than people who buy their way to victory or whales.
And yeah I agree the net gain off of high scoring in mini games is inefficient, but that also kind of makes you inefficient for high scoring in them, just get the bar to full then exit out. if you get a full bar you net around 59-69 coins and just leave and repeat. You could do what other people do, and leave Cleo at affection 0 and try to farm coins off of her while using the sleep free bonus to free farm minigames every 15 mins. (I didn't think of that and well I'm already too far ahead) Also if you want efficiency, line breaker has the most monetary gain for playing it longer, each orange bar = 1 coin and they come up frequently. (Though that's probably why you don't get much from the cat game since its the easiest of the games)
I totally agree with the energy, the energy system is problematic. Same with the decrease in the parameters, they scale percentage-wise. I find that having 100 vs 35 in any parameter; after sleeping will drop to 15 vs 7 respectively, so I don't like how that works.
The minigame part, I'm sorry to offend you, but the problems you are complaining about there... seem to be more issues of skill than actual problems. I've beat them all, rather the cat one is definitely the easiest, but all of them are beatable, the problem is that since it is a browser game, if your connection or pc isn't high spec, there is lag, and that has screwed me over multiple times.
I always get lust from gacha tickets, haven't spent $; but got them from the free daily ones and sometimes when I hit over 1000 coins I buy a normal ticket for 250 coins. (Although honestly I'd rather pull something useful instead of just lust)
Now on the topic of money, I honestly feel like you don't understand the money system, I agree with you, the game has shit money transition, but the values you're looking at is near impossible xD Most games tend to put a single gacha at around 3-5 bucks, so using that scale the diamonds should honestly be separate from lust dust and be put at 500 Premium for 500 Crystals approx. but not 1000 of both crystal and dust (though that would be nice). Maybe a bit less to match with the fact gacha tickets are only 250 crystal. The silver coins are easy to get imo, those I kind of agree with, I think it should be at least 2000, but honestly, thats the bona fide whale option, if you want to play for free, I would never look at that option xD
Anyways, on closing note, I get the feeling you are venting, and there is alot of frustration as a f2p player, but hopefully you can let it go. That's why you're f2p, you aren't spending money on the game anyways. Though I do have to agree alot of these hentai f2p games tend to try and money grab their players since its easy to grab people that just want sexy pictures etc. But so far I don't see too much of a problem with this game if you are willing to take it slow instead of trying to beat the game in a day.