Coming from someone who went to CIA ACCD and CIA i would say observational skills are the foundation for drawing but not limited or dare i say needed for design. Some people skip the still life phase and go straight into imaginary drawing and create masterful works without ever knowing the figure. I was advanced at observational drawing compared to my non and ID classmates. My preferred method of practice is to buy a sketchbook with a bulk of large white paper and put yourself in the most boring conditions go to a place where you know you can’t leave and there’s nothing else to do but sit and draw. I would recommend not to post any work online just focus on the work at hand if you spend 15 minutes a day drawing for 5 years you can become an expert. imagine the minutes you trade uploading the work for feedback when you could have been drawing, in time those minutes add up to hours of drawing time.
This method of practice is only for the truly dedicated or for those who do not have discipline of their own to sit down and make time for long hours of practice.