Most software engineers have a healthy circle of friends and social life.
> I hate having eclectic or traditional "nerdy" interests and getting a similar reaction.
It's not any different when an electrician, lawyer or a doctor wants to talk shop. Most people you will interact with don't have the same interests as you.
> I have no interest in turning off that part of my brain so I can fit into the sportsfan stereotype
Virtually no one fits cleanly into stereotypes. Stereotypes are useful for generalizing groups, not individuals. "Sportsfanning" is highly correlated with a rich social life, but you are confusing cause and effect.
> That I have nothing to look forward to but more of the same of this, and the few people I have contact with disappear in one way or the other. Sometimes I ask, why bother?
All of the rationalization about software engineering, "nerdy" interests is leading you astray. None of those are barriers to a fulfilling social life. Your social life issues are due to any number of problems. It could be depression, anxiety, it could be poor social skills. It is possible (maybe less likely) that you have little interest in deep social connections, but you have to evaluate carefully whether you are really unhappy with just a small online circle, or are you just worried because you appear away from the norm.
In any event I encourage you to think deeply about your situation. If you want to change anything, quitting software engineering won't help. It will most likely require a great deal of struggle. Depression and anxiety are not easily shaken off. Learning social skills like most things is harder later in life. I can assure you people in your position have improved, but only after taking stock of what is holding them back and seeking appropriate assistance.