I can't speak for others, but you didn't say anything weird.
However, designing an AI is very involved question. In my opinion, before you can think about AI, you have to design your gameplay mechanics because the AI will work based on that.
So the question is not easily answerable because it's too general.
In my opinion, it's better to start from the beginning. If you want to work on NPCs (ie enemies), create a framework for movement first. In your example, that's a top-down orthographic grid-based movement.
- Create obstacles on the grid.
- Create your enemy entities to move on the grid.
- Create a method by which you can instruct an NPC to move to a certain place using grid pathfinding (avoiding or moving around obstacles). This instruction can be pre-defined. It's only to make sure you can tell an NPC to move.
- Create methods which trigger an NPC to move to a specified place. For example, the trigger can be a countdown timer, or it can be based on a keypress, or it can be based on a player moving over a grid square. Also, for example, make the NPC go to a location if its 'health' is low or some other variable condition is met.
Those things are obviously basic and only related to movement. But when you succeed to achieving those basic things, I think you will have just enough exposure the concept of AI and start expanding those things to reflect the gameplay mechanics that you are designing. For example, you can include things like the enemy will consider closed/open doors for movement, or attack the player using ranged weapons if the NPC has any, or if the enemy's health is low, you can make him use some 'healing' item. But that is more advanced and I think you need to concentrate on the very basic stuff first.
When I was going my AI in my RND project (I have an RND project alongside my actual game project to test concepts), the movement was the most important bit because it was the one that was easily full of bugs. And it was made much harder due to multiple enemies who sometimes could not pathfind correctly amongst other moving enemies.
Hint: if you are still researching grid movement, I suggest using rexrainbow's Board system.