Can somebody help me understand why this does a water landing, like the old Apollo missions, instead of like the space shuttle that lands like a plane?

A big part of the reason is that Orion (and Apollo) reentry speeds are way higher due to the orbital mechanics involved in going to the moon and back. Today's was actually the fastest manned reentry ever attempted.

For reference the shuttle generally reentered at ~17.5K mph, and today's was 24K-25K mph.

It's not clear that we could build a craft with wings that could survive that. So then you're looking at adding fuel just to slow down, plus fuel for the weight of the wings themselves, plus fuel to carry all this extra fuel to the right place, etc.

The space shuttle landed like something resembling a plane, but it is more accurate to say it landed like a concrete brick traveling faster than the speed of sound.

Splashdown-style landings are the simplest and safest, parachutes are always good but adding water makes for another layer of safety (and of risk, to be fair, it could sink).

Wings and rudders and landing gear are very heavy. Then there's the flight control system in all its complexity, along with redundant hydraulic systems and so on.

Lot of the world is ocean & they basically decided the landing point the moment they entered the free return trajectory, 9 days prior - easier to shift the landing point a little to a different place in the ocean place with better weather tha. to switch to a backup airport.

With lunar landing flights they would still have to choose 4 days before, as long as they do direct return.

Eventually you want to break to Earth orbit (propulsively or aerodynamically) and board a dedidacted craft for landing. But till then water landing capsules work.

A Space Planes is needed to land at a runway like a plane.

Space Planes are not only much more dangerous, but are not ideal for this type of mission. They carry a lot of extra weight (wings) that would affect how much fuel is needed to launch them to the Moon.

Capsules are safer and more lean in terms of weight.

The Shuttle was not ideal in many ways. It was used so long not because it was the best option, but because Congress wanted it to keep it going for jobs.

Buoyancy is an easier equation to solve than lift.

Aerospace engineer here: The simple answer is that the Shuttle form factor is unnecessarily complex for this mission.

A small Apollo-style capsule that parachutes into the ocean has a simpler mission profile, which allows for simpler technical and operational requirements, which in turn reduces program cost.

Too fast. The space shuttle used to reenter sometimes over us in California. I remember in elementary school the entire building shook, and that was just one building! The amount of energy being dissipated is literally astronomical! If you've never experienced the sonic boom of reentry it is something to marvel at. It literally feels like an earthquake!