There never has been a very good option for big family and heavy travel trailer. Even the Excursions and 8.1 Burbs were stretched to their limits with a big camper and 4+ kids on board. This is because it is such a niche market. I think the average family now is <2 children, so a commonly available extended or crew cab pickup truck covers 99.99% of the market. Nobody is going to make a special vehicle for that 1-in-10,000 guy that comes in with a wife and 4+ kids in tow.
What killed the big engines and big SUVs was the new EPA economy and emissions standards. They weren't big sellers to begin with so the manufacturers discontinued them to get a big boost in EPA fuel economy ratings across their entire fleet.