FWIW, the DART orange line to downtown is about 50 minutes (seems like it used to take longer); TEX Rail to the ITC should be around 48 minutes.
TEX Rail is commuter rail largely because of cost. Double tracking and overhead wires are expensive.
Expensive light rail isn't as practical where density is low and stations are far apart. The TEX Rail corridor isn't very dense.
DART's Orange line is only 19 miles from DFW to downtown Dallas as I estimate from.
Wiki suggests the entire Orange line from Parker Road in Plano to DFW is 37 miles.
by roughly estimating downtown Dallas splits the line in half.....
Doing the math once again, 19 miles / 25 mph average =- 45 minutes., which is pretty close to the 50 minutes you posted earlier. FWIW, It'll be interesting what the exact distance was from DFW to downtown Dallas, I only estimated.
Additionally, there are two sections of railroad where the Orange line has ~5 miles between train stations (#1 DFW property and #2 Crossing the Trinity River). 5 miles station spacing is more like commuter rail spacing than light rail, but in these two instances there's nobody living there for a station to serve.