They’ve done a surprisingly good job of maintaining this scene, actually.

Rebels: Kanan is dead by now, and Ezra would be lost in deep space at this point. Yoda also wouldn’t know about either.

Mara Jade: 100% still a Sith Assassin right now. Also not Disney canon or anyone Yoda would hear about.

Ahsoka: This is the best candidate, since Yoda would know about her, and likely regret the decisions that forced her to leave the Jedi Council, making it weird to dispute her status as “Jedi”. The most favourable assumption is that he assumes she’s dead.

All said, remarkable protection of an Episode 5 made before episodes 1, 2, 3, multiple TV shows, novels, and sequels.

Does Mara Jade even exist in Disney canon? In old EU she certainly wasn’t a Jedi during ESB.

But yes, especially with Disney canon the number of Jedi or “former Jedi and not Jedi anymore but actually basically still just Jedi” running around has gotten out of control. I chalk it up to the original trilogy vaguely assuming the clone wars had happened longer ago than ended up being written.

None of those people exist