There are plenty of things a CEV could do better than the Shuttle, or at least, I hope it will.
For instance:

A fast to open or close hatch (like Apollo or even faster) if only for safety reason.

A sea level atmospheric pressure (if there had been a fire in a MIR in pure oxygen, all 6 astronauts would perhaps not haver survived it in 97) with a shirtsleeve environment for going up and coming down (perhaps a pressure suit like the Russian Sokol but not like the Shuttle astronauts).

Ingressing the capsule before liftoff at a later moment in the countdown, not forcing the astronauts to lie down too long.

A shroud hard enough and a rocket strong enough to withstand all kinds of weather paterns (temperature variations, rain, winds, etc..) at liftoff. Of course, a storm should better be avoided.

Easy and quick docking and undocking procedures; a spacesuit that's not too hard to get into and out of.

For landing, capabilities to land on the ground or on water.

Each time the Shuttle lands, it takes an hour for astronauts to get out of the vehicle! What if there were some kind of emergency?
The next spacecraft should make it possible to get out from only seconds after landing.

Raoul