How does the old saying go? The road to where is paved with good intentions? You could engage in moralizing against "carelessness" and "neglect" and presuming that a teammate somehow cares more about watching Netflix than doing their job (which they presumably outperformed other candidates to even get), and maybe that will make you feel better. You are the good, careful, model employee, and that other one -- they're careless, slovenly, apathetic and lazy. But if that's the case, how did they get past the door in the interview process? If the whole company is like that, why do you work there as opposed to a company where the bar is higher? Something does not add up. In all likelihood, your explanation is a rationalization and not the most obvious answer, which is that your process could be improved but it hasn't been because such investments are not viewed by your companies executives as improving the long term bottom line to be worth the short term investment cost.
Take a look at history and figure out how companies in the industry have solved this problem before by building more bulletproof runbooks, processes and tools. These companies, as they approach enormous scale, necessarily have to determine how to deal with employee reversion to mean. It turns out, surprisingly, that process eats good intentions and care for breakfast. You'd be surprised at how quickly those good intentions become useless if your company is successful and you hit hypergrowth and scale. It's ironic that for a profession where it is so tractable to automate away mundane or repetitive tasks, where we study spacetime complexity in data structures and algorithms, that we have so many practitioners that default to witch hunting and moralizing and seem unable to apply spacetime complexity or procedural analysis to their own software development lifecycle. I expect to see this trend change as our still young industry continues to mature.