And don't think that he was being a Lil reckless since he was an Edo and he knew he would regenerate after he got hit?
If zetsu said that he should've been able to dodge Sasuke rigged double demon windmil shuriken while in the middle of both( since he assumed he was healthy), you don't think that he can dodge rocks ? Lol
I don't see why he would be reckless since Kabuto's goal was to take control over him while vulnerable and use him against Sasuke. If it wasn't for Sasuke, Kabuto would have succeeded in that regard.
Being able to regenerate doesn't make you invincible to everything else. Kabuto wasn't aimed at killing, but controlling, and the only way to achieve that was while Itachi was regenerating.
Also the spiked came from all angles. I'd say that's a lot harder to dodge than the shuriken.
Regardless, the point is that he wouldn't be able to use it against Obito. Obito already knows all Uchiha Kinjutsu, which means he knows the weakness of Izanami and the process that is required for it to work.
As soon as Itachi yells "Izanami" in order to start the process, I'm sure as hell Obito would do something to counter that.