I'm from Texas as well and I'm simply not a fan of lean brisket, period. It really doesn't matter where you get the lean stuff, it's just not going to be as tasty as the moist brisket with all the fat. IMO. I mean we are talking about a "well done" piece of beef regardless. I'm sure WDW isn't using the most high quality marbled brisket to begin with, which is highly important when it comes to any beef product.
It's like comparing Outback Steakhouse to a fine dinning steakhouse, there is just a big difference in select versus high end choice and Prime 1 cuts of meat. In Texas, most BBQ places know they have to compete with other establishments around the area, so they are basically forced to use high grade beef brisket. At WDW, they have a captive audience, so cheaper meat = more money. They are appealing to people who just want a smoky flavored piece of beef with BBQ sauce slathered all over it, for the most part.
Although I'd put myself in the "I'm not a BBQ snob", I do always keep this in mind when I do choose to eat BBQ.
I've seen plenty of reviews that state the brisket is dry and not moist at Regal Eagle so I just assume the grade of beef is likely the issue.