do you have some suggestions about how this could be handle? Like, recommend games that I could look at? Overhauling the UI for the most part at this point feels almost impossible, but I really should do something about it
I mean, you already have TiTS and CoC as great example how text-based sex games could be.
First priority would be categorizing the areas in something like a map. So far you've made it that events can only be triggered from either journal or traveling to the submenu under each areas, which is honestly, not intuitive. Putting them under few submenus can very easily fix the UI clutter.
For example, putting the map access under [Move] menu and removing the [Return to Base] and [Visit Last Location]. You can put the locations under the [Move] option:
[Town], [Forest], [Mountains] and the surrounding towns.
Inside [Town] Menu you can draw a simple map with movement nodes, like [Castle] [Downtown] [Outskirts] each with their own minimap and event nodes ([Blacksmith],[Tavern]) so the players don't need to navigate a lot of dropdown menus inside dropdown menus.
Secondly, using the lowerside bar more than just to choose dialogue options or battle skills. Like in the slave management, surely there's a better way to display all of that information aside from the main screen? The sex option also should be displayed in a new screen, not shoved on the lower right side like that. Items and equipment, too, shouldn't be a dropdown menu from the side of the screen (most importantly, show players the stats of the weapon and not just put flavor text, because that means people won't need to calculate how much attack they gain from the weapon). Adding to this, there's no need for the character's status page to be displayed 24/7 aside from the three important stats (HP, Lust and Corruption).
Thirdly, explanations of how things works. There's virtually no tutorial on managing your captured slaves nor explanation what did what. I've tried to put a captured E-rank succubus as a whore which ate leftovers, sleeping on barracks and with no salary and putting a captured S-rank bandit as Hunter with High salary, sleeping on personal room and fed with fresh meal. Nothing tells you what these things would give you. Same thing with the other management options for the town; setting the priority for goverment to high doesn't change the main politics of Nepotism for over 200 days.