Actually, it's not impossible to do a good job of that with simple techniques. In a cave with a non-trivial labyrinth, there are some paths but after that the players are free to go to visit them in any order they want. You can absolutely design intrigue scenarios that way. I usually do that, and it's a technique that we perfected for LARPs (one out of many that we used when designing 2-3 days events for up to 250 people, free to go wherever they want on the site) and called the bumper plot.
The principle is that you have a series of "bumpers", usually NPCs but it can also be information site. They can be fixed or mobile, and they can react to some characters and not others. And they can sometimes react to one other. And you just let the PCs loose in that environment. Depending on the order of encounters and their choices, they can have very different adventures, but it's still fairly controlled because they need information to progress anyway. It is bounded and complete, and it will have at least a solution. Especially on TTRPG when you can easily take shortcuts and make some encounters happen (in a LARP, it's a bit more complicated because you need to track the progress of the PCs and maybe help them now and then when travel time across the site and the luck of finding the right people means that it could take a very long time).
It's not that hard to create such a scenario, and it's one of my favourite techniques especially when I'm pressed for time, I just create a few interesting NPCs with some information and let the players loose. Arguably, it requires more improvisation capability on the DM's part, but some of the best adventures are that way, especially city ones. I have been re-reading the Assassin's Knot, and it's build more or less that way, for example.