I'm a software developer with over two decades of experience, who started as a 2D 'tweens' animator.
Features are very hard to implement, and take time to do correctly. An eyedropper and a color palette, for instance, could take months to get out the door. Once you jump in, it's often a much longer swim than you'd estimate.
Serif has been top-notch in their approach, and going "Valve Time" is important when you care about what you're creating.
And, don't forget... this isn't a static design. We could spend a week on a logo and still not be completely satisfied with how effective it could be.
Now, add all the time and patience required to give a design form and function. This is what Serif deals with every second of the workday (and beyond that.) Looking at what they've done so far, I feel that once a new feature is released, they've released it while being proud of a job well done.