Tapu Fini is overall a better Pokemon but Toxapex is better on stall due to its reliable recovery, Regenerator, higher defenses and ability to lay Toxic Spikes. Tapu Fini's advantages over Toxapex are offset by the nature of stall, which diminishes how much it would otherwise outclass Toxapex on most team archetypes. Its Defog support is irrelevant when stall already has excellent hazard control, and Toxapex's passivity is not a huge issue on such a playstyle, especially when it has Haze to stop sweepers. In addition, Misty Terrain will hamper stall more than it will help it, as stall largely relies on status to wear down the opposing team.