> it’s a complete waste of time because nobody’s mind is being changed.
What you said can be true if you approach the discussion with an attitude of “I want to change everybody’s mind” instead of trying to get to some agreement and truth.
Not only stating an opinion is compatible with a constructive discussion that could lead to a mutual adjustment of opinions—in fact, stating your opinion is a precursor to having a discussion that can change it.
> It’s an unhealthy waste of time and that doesn’t truly hit you until you invest the time in talking to an otherwise rational person, provide the closest thing to proof of your perspective in a situation and then watch them deny it anyway.
The magic happens when one person realizes that another, obviously sane in every other way person can think very differently about topic X. Repeated exposure to alternative views from other people in your circles leaves no alternative except to adjust your own opinion on topic X.
Thing is, it’s tricky or impossible online. Aside from a handful of well-known people with some reputation or infamy, most of us only know each other as handles with no context. On the Internet, no one knows you are a dog or a basement dweller who lives with his parents and could never hold a job. Meanwhile, access to a group of like-minded people is always at your fingertips when you are online. However, when you are in a company of people who clearly are similar enough in what they achieved, in their choice to work for the same company, maybe good in their software engineering skill, etc., it makes their opinion something that may count.
Not being able or willing to freely exchange and consequently converge on opinions with people whom you routinely meet in real life, and only discussing said opinions in your respective online bubbles, strikes me as a path to having more and more divergent, incompatible, extreme opinions (which I rather suspect might have been happening a lot in recent years).