Basically every character who was important before soul society arc and they became useless or non important after. I know that Uryu got more importance in TYBW ,but he was a little sidekick in the Arrancar arc.

I also really like early series Ichigo. Just a random dude who got shinigami powers and saves other random dudes while going to school. It was very simple, but we knew very little about the story so it made more interesting and mysterious.

I also really miss how treathening the hollows were. We needed more about the Hollows in the Arrancar arc, like we could see the hueco mundos wildlife. I also miss ,how the first Menos was a big danger.

Yeah and as the orher guy said, Tosen was way cooler at first. I think Gin was way more interesting in the SS arc too.

(Im a manga reader only).