The reason for the "incompetent" service is that Instacart exploits it's workforce and as a former member of said workforce, I can tell you in all honesty that many of us have lost respect for this company. It's focus is on the bottom line for THEM and there is little to no culture of respect for either the workers or the customers. They are the epitome of our current narcissistic culture which puts personal and monetary gain above quality and human values.
Yes if you can afford it, it's convenient but know that there is little integrity in this organization.