I don’t follow everyone who follows me. I will follow back sometimes if I look and their content appeals to me, but a large portion of the time it doesn’t.
For me, Medium is a writing platform, not a social site. Yes, I do connect with other writers here but it isn’t my main purpose for being here. My main purpose is to write.
People use Medium in different ways. I don’t think it is wrong or suspicious that some writers choose not to engage. It’s still a good publishing tool.