To me, @BayView's example was about a story primarily about aging and impending natural death. Driving Miss Daisy, on the other hand, is about friendship and change, and while in that plot that change happened to be in large part due to age, the core thing--change--is something that people at many different ages can identify with.
I like the idea that something traumatic has occurred in a character’s life that interferes with his expected level of competency. If you remember the film “ The Verdict” ,where through the voice of Jack Warden we discover Paul Newman’s past as a top flight attorney that leads to a downward spiral to an alcoholic ambulance chaser. There is something of the Greek tragic hero that seems to work for me when I develop a MC. I like to place my MC in a situation where he has a final shot to redeem himself like a buzzer beater in a Championship game against North Carolina.Sorry I went to Villanova.
I believe you worry too much for the audience to care about your MC, just write the story and show it. Then ask an opinion about it. Like that, you will get an idea if your MC impacted someone. However my advice is simply this, make your MC flawed as possible. The more human he/she is, more your audience will relate to your MC. Plus the amnesia at the start of your story has to have a reason. Maybe your MC did a terrible mistake, and now is paying the price? Did... let's says her selfishness impact someone? I hope it helps
As someone who has only ever written song and poetry this is a question is struggled with myself. First, I read the opening chapter of books where I felt a quick connection to the character, but I think it's often just a chance thing. I connect quickly to people I can relate too and you cannot make a character relatable to everyone.