I've got a GX470 and a 5th gen, they use the same transmission I believe, but programmed differently. The 4th gen will hold 2nd gear around a corner so you can punch it and accelerate confidently with no dramatics. The 5th gen is so eager to upshift that it's never in 2nd gear unless you're manually holding the gear with the shifter, resulting in laggy response time and lackluster performance.
Add to that the fact that the throttle by wire has a certain amount of "I know you say you want to go, but I don't think you want it enough" programmed into it and the end result is a disappointing showing. Guys with the same engine in Tacoma double cab longboxes don't share the same complaints not because of the weight savings, but because of the different programming.
It's entirely possible the transmission issue is a direct result of the TBW programming, and may be drastically affected along with engine response with a product like a sprint booster or pedal commander. These products don't add any power, they change the way the power you do have is delivered, and those that have them have very good things to say about them. I will get one of these someday, the 5th gen is the wife's daily for now so it's not top priority.
With how hard the 5th gen pulls once you get the revs up, it has the potential to be a lot zippier feeling around town without having to manually shift gears. It's not that they don't have enough power, it's that you have to try to hard to access the power.