First of all, the findings are from a survey, and while we love surveys and tend to place a lot of weight on the outcome or results, a survey represents just a few people of those that characterize a given group - regardless of the nature or general character of that grouping. Sample size has a lot to do with results also.
While the results of this survey may be accurate and really do apply to the Millennials generation as a whole - let's say that they are - there are several ways to interpret and use this data.
First, some of this age group is still in college and the oldest among them is just in their 30s. A lot can change in their lives over the next 30-40 or more years. If we think back to some of the attitudes we had a couple of decades ago - things we said we would never do or something we said we would always do - we may find that our attitudes have changed. Times change, people change, and our attitudes change.
Part of the question has to do with the way it is framed and the way it is interpreted by the younger generation. Since may of them have yet to purchase their first home, and a large number (a record number actually) are still (or again) living with their parents, it's entirely reasonable to hear that they can't think of themselves living in a home long-term. Also, the idea of a forever home does not mean that it needs to be purchased as their first home.
So many of us don't know what neighborhood we will want to live in or what type of layout we will want in a home until we have owned or lived in a few different ones. It is rare (but not unheard of) that someone remains in the first home they ever get. Some people make a great initial decision, and some people get lucky with their decision. Most people move once or twice, if not more, in their lifetime.
Another thing that we are overlooking in this premise is that the forever home is about aging in place, but so is living successfully and well in the current home - at any age, income level, physical ability, outlook on life, and other factors. Aging in place means doing well in the present home. If that home turns out to be a long-term residence, or if it is acquired with that in mind initially, then it becomes what we typically think of when we speak of aging in place. Nevertheless, we don't have to wait until our 50s, 60s, 70s, or beyond to age in place. It can begin now.
Still, projecting ahead a few decades to suggest what someone might or might not want to do is a lot to ask for someone who is just embarking on their adult life. It's not surprising that people aren't able to embrace the idea of having a long-term home - whether that is the initial home purchase or a future one.
Millennials are the largest generation in America, having eclipsed the Baby Boomers, and it's possible that they may redefine how they want to use their homes. For now, the Boomers definitely are wanting to age in place, and it's likely that many of the Millennials who don't think this is such a good idea now will change their minds over time.
Even if they don't have a long-term home because their attitudes don't change, universal design treatments and visitability fixes that they make to homes - or ones that are made by current owners to homes that they might eventually occupy - will mean that they are going to have homes that offer them a safe, accessible, comfortable, and convenient way to enjoy those living spaces.