Throwing more horsepower at what some think is a problem is not that simple. It's a fine line between making them too hard to drive which leads to a little passing single file racing clean air fest type racing, and being able to have decent passing and side by side racing with the fast cars being able to come from the rear to the front. I have no problem with Nascar sneaking up on it instead of taking the blunderbuss route. Leaving the most important factor aero out of the equation where more gains than horsepower when at speed occur leaves out a lot of a complicated number of factors.
For the record, a lot of the mid 2000s-mid 2010s California and Michigan races that were considered pretty tame are becoming "cult classics" when talent in the series was at its peak and the cars were entering the turns at 205mph+. I think the fan base is slowly turning towards wanting more speed and driver skill than needing close side-by-side racing