I've been scouring the web for good pathfinding algorithms, and I came across context-based steering. Turns out, someone had made a really good project on it, so if you need to add intelligent enemies with smooth movement, here's the project:

https://scratch.mit.edu/projects/994663693/

I prefer this one over griffpatch's version because enemies rarely clip into walls with this version and have much more realistic movement, griffpatch's pathfinding may have robotic “staircase” movements in place of diagonal movement and may take a slower path directly to a target. It's better for tower defense games, but I'd say this project works much better for real-time games such as zombie shooters.

(This isn't mine, but it's really useful and has helped me out a ton)

If anyone has another really good pathfinding project or one that they've found that has really smooth movement, feel free to put it here!

Another great thing about this is how the enemy stops pursuing you after they lose sight and have no leads on where to go. You can add a simple wandering script to deal with this.