Lots of homeless on that train in early morning and late at night, but not too bad in the middle of the day IME. My normal way to the airport during while in Dallas 2009-2020 (and a couple of months in 2021).

There is also Light Rail (ya, train to city is not really proper use IMHO) to Fort Worth. Best part of the Metroplex (as greater Dallas / Fort Worth is known locally, much like Chicagoland in greater Chicago area) is Fort Worth, and of the twenty year or so (on and off) that I spent in Metroplex, Fort Worth was the best.

Deep Ellum ..... ya, it eclectic, but in many ways, there's no there there unless you are into the clubs that are there. Downtown Fort Worth, OTOH, is walkable and kind of fun.

Oh, and the "train" to downtown Dallas takes an hour, runs every 20 minutes. Despite having an urge to try the Fort Worth light rail version, procrastination got in the way, and I never tried it, so have no firsthand exerience. Dallas light rail departs from Term A, Ft. Worth from Term B (IIRC).