Mainline mario games do not have anywhere near as much plot as mainline sonic games have had since the jump to 3D and again, the critics don't even matter in this case so it frankly doesn't matter to keep going on about it. They're going to keep pumping these out over the next 15 years.
And no that's not why we've had so many bad adaptations. Studio mandated changes to the material in an attempt to appeal to wider audiences has been the biggest hurdle. See Assassin's Creed, Doom, Hitman, Uncharted, Warcraft.