I am no longer a member, having resigned a few years ago. I do not watch general conference, but it is impossible to avoid hearing about it as it dominates social media, the local news and family/friend conversations. While watching the news coverage, it seems that almost every clip they played was about getting those who have left to come back. Was that really the dominant theme?
No, not really. I was talking to a couple of friends yesterday evening about what we all felt the dominant themes of conference had been, and that didn't make any of our lists (we each named 3-5 items).
And did someone actually say that you should ignore any "not interested list" a person may choose to be on because "people change?"
No, not at all. The quote you are thinking of was from this talk:
https://www.lds.org/general-conference/2019/04/media/session_1_talk_10/6023381089001?lang=eng
It came with regards to a story that Bishop Waddell (counselor in the presiding bishopric, I believe) told about his brother Mike who had not been active in the church for decades, but who decided late in life to rejoin the church and literally hours before his death from cancer was ordained as an Elder. Bishop Waddell expressed great appreciation for a man named John who had been a friend to Mike and had helped him through the tough situation. I'll transcribe the exact quote from Bishop Waddell (starting at about 4:14 in the video linked to above):
(start quote)
Speaking of the Savior, President Nelson taught that "Because it is His church, we as His servants will minister to the one just as He did. We will minister in His name, with His power and authority, and with His loving kindness."
In response to that invitation by a prophet of God, remarkable efforts to minister to the one are taking place all over the world--in both coordinated efforts, as members faithfully fulfill their ministering assignments, as well as what I will call impromptu ministering, as so many demonstrate Christ-like love in response to unexpected opportunities.
In our own family, we witnessed up close this type of ministering. John, who was Mike's friend, ministering brother, and a former mission president, used to tell his missionaries that "If someone is on a list that says "Not interested," don't give up. People change." He then told us, "Mike changed mightily."
(end quote)
In my opinion the quote is very much saying, "Don't give up hoping for the person to change." It is certainly NOT saying, "Don't give up pestering people who want nothing to do with the church."
To continue with his remarks, he then goes on to say:
(begin quote again)
John was first a friend, providing frequent encouragement and support. But his ministry didn't stop at friendly visits. John knew that a minister was more than a friend, and that friendship is magnified as we minister. It isn't necessary for someone to be suffering, like my brother, from a life-threatening disease, in order to be in need of ministering service. Those needs come in a variety of shapes, sizes, and conditions. A single parent, a less-active couple, a struggling teen, an overwhelmed mother, a trial of faith, financial, health, or marriage issues... the list is almost endless. However, like Mike, no one is too far gone, and it is never too late for the Savior's loving reach."
(end quote)
So, to add to the context, we should help people with whatever their trials are. And again, the quote is still not at all in the context of pestering people. But even better that reading my transcript here would be for you to listen to the talk and judge for yourself. It's less than 12 minutes long.