First we will get the x, y coordinates of the camera relative to the Viewport this will ensure that we'll have the edges of the camera view no matter the aspect ratio of it.

Ps. I use this Range struct just because i prefer to read min, max instead of x, y in this situations where i have a min, max value.

[System.Serializable]
public struct Range
{
    /// <summary>
    /// Returns a random value between min and max.
    /// </summary>
    public float Value { get { return Random.Range(min, max); } }

    public float min;
    public float max;

    public Range(float min, float max)
    {
        this.min = min;
        this.max = max;
    }
}

public static Range VerticalLimit;
public static Range HorizontalLimit;

public static Camera MainCamera;

private void Awake()
{
    MainCamera = Camera.main;

    Vector2 __minLimits = MainCamera.ViewportToWorldPoint(new Vector2(0.0f, 0.0f));
    Vector2 __maxLimits = MainCamera.ViewportToWorldPoint(new Vector2(1.0f, 1.0f));

    VerticalLimit = new Range(__minLimits.y, __maxLimits.y);
    HorizontalLimit = new Range(__minLimits.x, __maxLimits.x);
}

Then we can simply check if a passed point is inside within the min and max Range of the camera view world boundaries.

public static bool InsideCamera(Vector2 p_position)
    {
        if (p_position.x < HorizontalLimit.min || p_position.x > HorizontalLimit.max)
            return false;

        if (p_position.y < VerticalLimit.min || p_position.y > VerticalLimit.max)
            return false;

        return true;
    }