After finishing I felt I needed to add this to preface the absolute WALL of text. This was obviously a word salad that may be much longer than it needed to be but since you said you didnt understand the problems that some posters are having with the system other than vague complaints I felt I'd at least tell you my experience to the best of my ability.
Thanks.
Cant speak for others but when I first started to play I did what I usually did when I played years ago. Get clothes ready for the job they were probably going to get trained for unless training led to a special trait for another (wouldnt let them wear it till they would do simple tasks though), get a collar that didnt negatively affect a major stat like the steel one, may or may not brand on day 1, then go home and explain their situation.
A reasonable approach.
Then depending on their personality and the trainers stats it really felt like it was difficulty appropriate. A high level trainer, or maxed like in my tests, would usually be able to get at least a neutral or 1 positive result on something as simple as basic household chores barring maybe the more proudful slaves. If not then with a single punishment or two they would then produce the same low, but still visible, results and the more prideful ones would be the potentially even week's worth of a challenge as they had to be and the punishments reflected it. But I never once was able to recreate the same thing in the over 4 hour tests I did when I started playing again, even with the most docile slaves (unless they were already mindbroken with "Sanity" to begin with), and it just really shouldnt be that difficult for literally every single person as people are typically pretty obedient especially when thrust into a society that isnt shy about its cannibalism (namely of slave meat) staring you in the face when you head to the local market or the beings that are presented in front of you at your auction and knowing what they would have done with you as they are not shy with shouting it out.
I just started a custom game with maxed slaver stats and obtained the following slave from the market (the first one offered):
Normal difficulty. This slave is Willful, Clever, Lively, and Proud. Look at the text below her rules - her psychological state is very much against obedience at the moment. This slave started with 1 point of spoil, too, making her even more inclined to disobedience. This is how I dressed her:
This is sub-optimal. You could also give her a hijab and rubber gloves to boost her cooking more. Explained her position, then tried to give her a cooking lesson. She refused. Punished her with a verbal chastisement. Tried cooking lesson again, refused, punished with a slipper spanking. She "fought back" but was too weak to actually start combat, so just got some bruises. Tried again, refused, punished with a naked walk. She was depressed and down to half a star of energy at that point. Put a tattoo brand on her along with the collar so she would be returned if she managed to escape. Encouraged her, sent her to take a bath (by herself) and ended the day. No rules assigned; she was already fearful from the punishments, so no risk of spoiling her. She ended the first day with a sullen mood. Day 2, encouraged her again, explained her position, asked her to cook, refused, 3 guilt. Punished with threaten tortures (psychological pressure). Cooking lesson again, refused, punished with living canvas (shaming). Cook lesson again, she agreed to do it, but her motivation wasn't high enough to gain any merit:
At this point, as is clearly stated in the screenshot, you need to focus on improving her motivation; she is no longer refusing outright.
So here we have a fairly resistant slave that has reached the obedience threshold for training cooking on the second day. She experienced a couple of verbal punishments, a couple of shaming punishments, being spanked one time, a couple of lectures and some words of encouragement, and had one night to think things over while sleeping on the floor (with a bedroll) and wearing a slave collar.
What would you change here?
When I eventually moved on into trying different techniques that werent overly "spoiling" (not the game mechanic but in a immersive character decision way) like undeserved comfortable clothes on day 1 or repetitive tedious exclamations like using threaten or encourage every single day things would go into a Sanity spiral. Slaves that didnt have at least 4+ hearts would fail, need to get punished, fail again, leading to more punishment, and since theyre certainly not doing any chores whatsoever the player must make food, clean, and bathe themselves so youre likely out of hearts or getting close to it by then so you have to end. This would continue until either Sanity pops up or they finally begin to complete tasks in a positive way but hardly at all and at that point pride/nature/temperament are likely close to being near Sanity levels as the repeated decision on refusing to sweep a floor or be thrown on the street in a world that clearly thinks less of them than dirt is just too hard of a concession to make apparently. So then theres an attempt to send them to the hot spring or other rewards to raise stats to get out of or away from Sanity. But then they would become spoiled as they didnt deserve these rewards for subpar results making them once again refuse completing tasks leading to more punishments and back into mind broken status.
As the tutorial clearly explains, one of the challenges in training is to build up obedience without letting the slave develop too much angst (despair). Letting the slave be in a bad mood for a few nights won't do much harm (and may reduce spoiling faster), but if you don't prioritize keeping their mood up, you're shooting yourself in the foot.
Undeserved clothes on day 1 is a matter of perspective. Does it serve your purposes for the slave to feel exposed, naked, and cold? If the consequence is depression, perhaps not. On the other hand, if the slave is spoiled and in a good mood, maybe you want to knock them off their high horse with some discomfort, in which case spending a night naked on the cold floor without a bedroll might be just the thing.
After another poster had told me they could do it on day 1, I then finally dropped any and all attempts to play as I felt was realistic in the situation and treated it as a numbers game. Immediate branding, comfy clothes, repetitive but apparently now necessary daily threaten and encourage lines, and daily aura strengthening spells even though my stats are maxed so this really shouldnt be necessary, and they would now complete basic tasks within a day or two as long as I never went away from that formula for a week or two for obedience to grow and finally allowing for nonregimented play. But thats boring for me and far to "meta" as I was told to adapt to in relation to the inarguably more abusable yet still (as I believe it to be) more realistic older versions to have been. Now again this isnt an attempt to rag on the people working on it, in my previous posts Ive said you can tell that theres a real attempt at trying to get around older cheesy strats and and to coax people into the magic and alchemy side of things by having to look at a slaves aura during training but before I never needed to put a single level in magician in my normal custom games as the interaction with the slave felt real enough to gauge what was needed as you played. Now it feels artificial and not reflective of the stats shown to the player as they look at the trainers stats and to make a training plan appropriate to their level, but instead just a simple numbers game thats just as abusable if you choose the "correct" meta choices. But thats just how it feels like to me.
Notice I didn't use Threaten and didn't cast any spells in my above example (no aura strengthening). The slaver also didn't have any clothing except the default worn clothes, which could've boosted his aura more. You don't need to read the aura (although it certainly helps) - you can get enough information by asking the slave questions, such as "what do you think of me?" and (once the slave is a bit more obedient) "how are you feeling?" to figure out what would be the best way to boost her mood.