I don't know that I'd ordinarily go out of my way to complain about it - there have certainly been worse seasons of animation - but season 3 felt quite boring. It didn't feel as though we really got to know the new characters all that well yet everything took forever to happen; I think it could have trimmed off a couple of episodes' worth of dramatic reactions and vacant staring from the mist guy and come across as much tighter overall. There was nothing wrong with the content, it just wasn't strong enough to hold my interest for an entire season and took way too long to get into the meat of the hashira backstories.
Season 2 had more clearly-defined characters (the actual villagers were largely pointless in season 3) and a more charismatic set of new friends/enemies, so I had a much better time with it. I am also one of the weirdos who like Zenitsu (Inosuke, however...) so I missed his inclusion in season 3. Separating Tanjirou from the others was fine, but given how samey the episodes felt I would have enjoyed more glimpses of what was going on elsewhere to help break up the endless fight scene.
R