The T-tail associated with rear engines requires extra structural weight of the tail... And bad stall characteristics of T-tail airplanes required "stick pushers" for certification.
And to those of you telling us that the VC-10 is a nice looking airplane, we all have our preferences... So, my favorite airliner is the SE-210 Caravelle for the looks.
Note that rear engines do not REQUIRE T-tails. Caravelle manages with +-tail and two rear engines. Jetstar has +-tail and 4 rear engines. And Falcons have +-tails - both the twins and trijets.
What would you call "next generation regional jet"? CRJ has been around for a long time. So has ERJ. E-jets, Superjet and Mitsubishi Regional Jet are underwing twins. That leaves ACAC ARJ21 as the only new rearmounted twin in development - or else it is another DC-9 model. Oh, and Tu-334, but its first flight was long ago.