I love fantasy worlds with giant wildernesses that are full of ancient ruins and fearsome monsters.
Sure, but there's a problem with that scenario - if those ruins are close to populations, they'd have been explored already. If the monsters were near people, they'd have been dealt with, too, or the population will have collapsed. It doesn't make sense as a status quo near people.
The most successful frame for this I have seen recently is to frame the campaign as being in a time of some change. For example: The Dragon of Icespire Peak. I have played, rather than read, the adventure, and for us it was framed in the following way: The PCs come to town, where the eponymous dragon has recently come to the area.
Now, the 1st level characters are not up for just going and taking on the dragon, but the dragon's arrival has changed the situation in the nearby mountains - various adversaries move out of the mountains to keep away from the dragon, and move into some of the local ruins, and start causing problems. The locals are not up to dealing with monsters and bandits and all, because they haven't eeded to be. The PCs walk into an emerging situation that more or less comes to them, rather than they wander around looking for trouble.