Everyone seems to think this is only an affordability issue. I think everyone is forgetting that there is a huge amount of people that DON'T want to live in or near a big metro area. There was a time in my 20's that I enjoyed being near all of the lights, sirens, and and amenities that a major metro provides but as you age you start to understand that it's really over rated.
I grew up in small town Kansas and have lived in some big cities after I graduated college. There is no comparison in the quality of life. small town, country living will ALWAYS beat the city life. You don't have to agree with that and it's not anything factual, but it's important to understand that there are millions of people that would agree with it.
I choose to only invest in small towns because I am seeing more and more people choose that life over big cities. In fact, I just had a young family from the Seattle area move into one of my houses in a small town in Kansas of about 11k people. I've had multiple people from metros all over the country reach out to my houses that are posted for rent on Zillow that are moving to small town Kansas. A lot of people want out of the city.
Sure, rising population metro areas are a safe bet when it come to investing. Location absolutely matters. But for a lot of younger family's a small community, starlit sky's, and the sound of nature are more important that constant sirens, Uber, dog spa's, and 100 different coffee shops or microbreweries.