I love the look of CO, and I loved the updated character creator and the way the game fades to black and white if you go too far off map. Unfortunately, that's all I love about it.
Even before they locked away fully customised characters behind a massive paywall, I had big issues with how the game plays. Characters run and move like they're trying to fight their way through treacle, the basic control system doesn't feel intuitive (compared to other MMOs, anyway), and the early instanced missions felt like long corridors without very much going on. Also, the stories and characters in CO just... didn't grab me. Maybe that's personal preference, but it felt very hollow to me and the few characters I did meet felt like they'd been phoned in.
More action-based combat sounded like fun, but in reality I don't think it was handled all that well and felt clunky. Compare CO's combat to the action combat in Wildstar, for example, and it's easy to see where CO falls short of what it was aiming for. In fact, 'clunky' sums up a lot of CO for me, and sadly it kind of kills a lot of the things that were basically good ideas.
I feel like if CO was made today it would be a brilliant game, but it wasn't. It sort of sits in an in-between place in the MMO time-line, and I honestly think it was too ambitious for what could be built at the time.