Change Creates Tension Creates Adventure

Making adventures can be hard. There is a reason all the major RPG producers sell pre-written adventures. There is a reason the DMSguild exists. There is a reason you can barely throw a rock in the RPG side of the internet and not hit any number of adventure idea/seed generators. There is nothing wrong with them. In fact, a lot of them are really good with some amazing adventures I'd imagine the vast majority would never consider let alone be able to pull off unaided.

However, it is also easy enough to make your own adventures with a little bit of thought. And if you consider this when making your world or designing your setting, you can bake in near endless sources of adventure ideas into the world itself. What is even better when you do this, is the adventures stem naturally from the world which makes it feel like the setting and world is a part of the adventures of the campaign, as opposed to just the backdrop for where it happens.

Change Is At The Heart Of Adventure
Change, and the seeking of it therein, is at the heart of every adventure that happens. Lost Mine of Phandelver happens when the local goblins have a change in leadership with the arrival of a drow wizard with a plan. There is also the resistance of the town to the gang that more or less took over Phandelver, which is more kicked off by the arrival of the PCs who are a threat to the gang (and thus a potential agent of change.)

The Jewel of Yavin for FFG's Edge of the Empire is a Heist story around a major gambling event. In that there is change on Bespin with the arrival of all the gamblers, all of whom have their own desires (mostly to make money) and the PCs are there to try and change ownership of the jewel of yavin to themselves (or their patron, depending on how you run it.)

Much of Curse of Strahd is Strahd toying with the PCs because the change they bring is entertaining. The PCs themselves are looking to be agents of change either in overthrowing Strahd, or breaking his hold enough they can leave.

No Change Goes Unresisted
The thing to remember with change is the mechanics of it are very simple. Someone, or thing, wants something and so takes steps to make it happen. The thing is, no change is unresisted and that is where the story goes. For personal stories the resistance can be internal. For example, if I want to lose weight I am going to face resistance from my body as the actions needed to lose weight involves changing established patterns my body is fond of. There is also resistance from the natural degradation of my body as I age and that the actions taken will be further drains on my "energy pool" already divided up among my various daily tasks I do.

External change is even easier, and where most adventures happen. There is always someone who benefits from the current status quo, and people looking to make changes disrupt that so there is resistance. A gang looking to make more money will have resistance from rival gangs that have their markets encroached on. A movement to promote the rights of a suppressed group will face resistance from the people who benefit from that group being suppressed. A wizard looking to build a tower near a city will face resistance from the people who don't want a wizard tower disrupting their view, or worried about the dangers of a nearby wizard tower.

Change Means Two Sides and Tension
The push for change, and resistance to that change creates tension. That also gives us two sides and tension between them. And that more or less sounds like an adventure to me. Even better, it is one that can be used multiple times in multiple ways from both angles.

Take the Wizard Tower for example. The PCs could be hired by the Wizard to help make the case as to how the Wizard can help the town. Either by talking to the people in the city, solving problems the city may have with local monsters/threats, or something else. Alternatively the PCs could be hired by the PCs to investigate the tower and find out what the Wizard is actually up to. Or the PCs could come in to find the local townfolk looking to lynch the wizard. Or the Wizard could need help because a summoned demon escaped, and if it gets out that the Wizard did it that could ruin him since he'll lose the ability to build his tower and all his money is already tied up in it.

And then there are the stories around it. People, monsters, and other threats coming because a wizard in the area means magic and thus likely treasure. A rival wizard/city/kingdom feeling threatened and attacking before they get attacked. Someone bringing a curse into the area while seeking the wizard's help to cure themselves and not realizing they're contagious.

Build Change Into Your Setting
Build moments of change into your setting. At worst you have a backdrop to other stories you want to tell. At best, you have a potential endless source of inspiration for things that can cause adventures and interactions to happen in your game.