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.
Ahsoka has not been a jedi since she left the order. She's just a warrior who has jedi skills due to formerly training as one.
100%, but ideologically she's every bit as much a Jedi as Luke is here. He's not had any formal induction to an organization, so that can't be what Yoda means here.
Yoda is also shown quite clearly regretting the kind of stagnation he allowed in the Jedi Order, which is exactly the reason Ahsoka was put in the hard situation she was. The Clone Wars very much set up her character as an emblem to show the rot that allowed Palpatine to rise, which Yoda acknowledges and regrets quite explicitly there. It's not a ridiculous inference to assume he respects her and would validate Ahsoka as part of the "good side", which is about all "Jedi" can mean in this context. She even explicitly and repeatedly tries to turn Darth Vader.
Anyway, I do agree in that it's not a massive plot hole or anything, but I'd say that if we're ever explicitly shown Yoda meeting Ahsoka pre-Empire, this scene will be weird.
Yoda actually did have contact with both Kanan and Ezra a few times. It's quite possible that he sensed Kanan's death and was aware Ezra was out of the galaxy.
Reminds me of watching a chronological cannon timeline of Bruce Wayne's life and there ended up being like a dozen superheroes, including two future versions of Batman, who were watching the Wayne's get blown away in crime alley.
Seems cool, would you have a link?
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.
The Expanded Universe is not Disney canon. The Solo kids, Chewie, Palpatine clones, Thrawn, none of it played out the way it happens in the books. It is theoretically possible that between The Mandolorian episode where we see youger Jedi Master Luke, and the end of The Force Awakens where we meet Old Jedi Master Luke, that Luke met Mara Jade, got married, and fathered a child. But there was no mention of it in the new Disney trilogy or associated TV shows. So I would assume she doesn't exist until someone adds her to a story, and even then I wouldn't assume she would have the same role.
I think they could conceivably tie in Thrawn with the efforts to clone the Emperor with the ST's interpretation of him coming back still. It was hinted in Mando already and I could see Thrawn being emboldened by the Emperor's return to start planning for the First Order or the dark fleet.
Mara Jade is in Star Wars: Masters of Teräs Käsi which will forever be complete and inarguable canon just like the Holiday Special.
