Yes, I know large amounts of TCW was made before the uyout, but as I said TCW tended to ignore prior work anyway, and more pertinently, the tail end of TCW which is relevant here, was primarily produced during or after the changeover with the knowledge that it would be canonised.
Maul flat out doesn't meet Anakin either, so that feels like a non-starter for Grievous comparisons, and I don't see why Dooku has to question his master to the same extent Maul does. they wrote the Maul plot for what they wanted to do with Maul, and if they wrote Dooku plot it would be tailored towards, well, Dooku. the Maul plot's narrative arc at the end of TCW isn't some written in stone inevitable thing they have to do. My point is simply that for a story nominally pushed as the primary story of the clone war period, it's bafflingly devoid of two of the biggest player in the late stages. Anakin and Obi-Wan are pretty established characters as well, but they don't almost completely fuck off from the second half and are inherently part of the main plot even though they aren't involved in the final battle itself - it takes them right up to the point of leaving for Ep3.
And just.. no, no Maul wasn't interesting IMO. He still had no personality, little depth or direction, and spends most of his time bouncing between disconnected story elements and charcaters brainlessly screeching about Kenobi and leaving a congaline of aborted storylines in his wake. The ending duel with Obi-Wan is a joke, because it has nothing behind it, no depth to their relationship because they have barely encountered each other. An inecredibly flat character stands across from his alleged nemesis - who incidentally is otherwise entirely absent from Rebels - for about a minute after stumbling around in the desert for a purposeless amount of time, and then dies in a second. It's the epitome of fake profundity and episode length bloat. I'm generally an advocate of taking more time when necessary and not super into the frenetic pace of a lot of modern media, but there needs to be something meaningful behind that time taken. The whole Maul story could have been one, maybe two TCW episodes and accomplished the same, without the sporadic all over the place mess it took to arrive there. Greatest moments in all of Star Wars? lol
Maul exists for no other reason than to look cool and do cool things. And pretty much only Episode 1, and the final two TCW episodes, realise that. He's a brainless setpiece, not a deep character, at least not as Lucas and filoni write him, despite their rather evidently emerging delusion otherwise.