Five life is quite a lot to pay in todays Commander metagame, but this feels costed just right as something that will cost life on crucial or early turns and otherwise just cost three mana
The +2/+2 boost and hexproof from mono-colored spells make it tough to answer, and the more colors your creature has, the cheaper it is to equip
Even if I've convinced you that incarnate is a good thing when designed well, I still need to defend lack-of-variance
The most popular Commanders need to get through 2020 without reprints, and then Ill relax
For that reason I think Niambi is fine as a commander but better in a deck that has access to Black, such as Sisay, Weatherlight Captain
Sorcery Color tag templates(None) Chatterstorm Create a 1/1 green Squirrel creature token