Even if Mace cannot use Vaapad he still has achieved mastery in normal Juyo, which would be in the same tier (maybe even higher) as Maul's. He's also stronger in the force so he could probably solo this with some difficulty. Add in another master like Plo and Maul is done. I am not downplaying Maul in any way but he's just outclassed against two of the best clone wars era jedi.
I believe you underestimate jedi who don't live in active warfare and surely Mace and Plo would be stronger during the clone wars but not by such a large margin. Younger jedi like Kit Fisto, Quinlan Vos or Obi-Wan were forged during the war, achieving mastery during it, whereas older ones like Mace, Plo and Ki-Adi Mundi already had a ton of experience before.