There are lots of reasons someone like you might benefit from a framework, but this one jumps out immediately:
> I already know how to implement core functionalities when needed (e.g. CSRF, user permissions)
Even if you know "how", this is still wasted time on your part. These are solved problems.
Particularly when it comes to security features like CSRF, relying on yourself to implement it sounds like a major footgun opportunity. When you use a framework that has this built in, you have to try really hard to bypass these security features. You barely even have to think about how to implement it.
> I already know how to implement core functionalities when needed (e.g. CSRF, user permissions)
Even if you know "how", this is still wasted time on your part. These are solved problems.
Particularly when it comes to security features like CSRF, relying on yourself to implement it sounds like a major footgun opportunity. When you use a framework that has this built in, you have to try really hard to bypass these security features. You barely even have to think about how to implement it.