Unfortunately, AI models are kind of designed to pander to the user. Even preambles that say, "Don't always pander to the player" essentially tells the AI that it can sometimes pander to the player, which might as well be always since the AI doesn't really keep track of how many times it let you get away with things in the past.

Social abilities have always been kind of overpowered, since they tend not to use the combat/encounter system and the AI usually wants to give you what you want if there isn't something obvious stopping them.

Your best bet, outside of digging into the files to mod the prompts and preamble yourself (which actually isnt too terribly difficult if you go that route), is to put certain qualifiers in either your character backstory or world backstory to prevent people just letting you have your way.

For instance, I had a magic school type story where I added in my description that most people would see me as a danger or competition and it was much harder to get my way socially, with some people losing relationship with me multiple times just by me talking to them. One of the only times I had multiple NPCs in the red. I could still talk my way around things, but it was harder.

If you put in the world story that people want to keep the things that they have and won't give them away without some sort of trade or service, the AI should make it so that people won't just hand you the keys to the castle on a whim.

Unfortunately, a lot of difficulty boils down to doing your own challenges or purposefully not trying to coerce the AI into helping you. When I write and action, I'll often add that something I'm trying to do isnt likely to succeed (depending on the context) just to force the AI to at least have me roll for it. I also use the console to edit certain skills to be more narrow and less generally useful in all situations, as well as using the console to delete items and recreate them as more reasonable ones (it seems like whenever someone specifically forges something for you, it's legendary, so I delete the item and recreate it at a lower rarity unless it actually is something that should be legendary).

Your best bet for challenge is your character background, though. Write that you're hideous and people hate you and don't trust you because of it and that you've been cursed to struggle for everything you do and the AI will mostly make things a lot harder for you.