So to be very frank about the situation, I think he is sort of stumbling into the fact that New England has a kinda unusual history when it comes to engineering.
Not to get too bogged down in history, but the study of engineering as we know it started with the “modern university” model that arose in Germany, and came to the US via what became the University of Michigan. That model was then the core of what became the land grant system, and many of the great engineering powerhouses are land grant universities, or at least large flagship-equivalent publics of some sort. Others were privates founded during or after that period, but on that model, like say Stanford.
New England, though, already had a well-developed set of “classical” colleges before this all started. MIT and Cornell, however, were founded as land grant universities, even though they retained a private structure (mostly, it is complicated with Cornell). Some of the classical colleges sort of stayed evolving on that classical path, and those include some famous LACs, mostly without engineering (although not entirely). Others, though, morphed into modern universities, but the degree to which they actually did engineering was quite variable–and it continues to be a variable to this day.
OK, so then in New England, there are also public land grant universities, and they typically do have engineering, but . . . because of the existing competition from private LACs and what became private universities, there was sort of a regional attitude about the top kids not necessarily going to these public colleges. I think that has been changing, and in fact I think sometimes OOS engineering kids are also looking at some of these colleges. But still, there isn’t really anything quite like a Michigan, Illinois, Purdue, Cal, Texas, Georgia Tech, or so on in New England. That “slot” is basically filled by MIT and Cornell (I know it isn’t in New England, but still).
OK, so, what to do if you are an engineering kid who wants to be in the mountains of New England, or close, but either can’t get admitted to Cornell, or just don’t want to go?
Well, you could ignore the people who say you need to go to a super reachy college. Like, go to Vermont, New Hampshire, or UMass Amherst (if you think that is close enough) if you prefer public. Or, Clarkson, RPI, or Syracuse if you prefer private.
But you could also go to Dartmouth. As you note, though, there are some potential downsides, and I personally would not get caught up in the idea more selective = better for me when it comes to engineering (or really in general).