A display cabinet should earn the right to hold things behind glass, and most of the ones I see in people's dining rooms haven't done anything to deserve it. The good ones come from a time when a cabinet was built to outlast whoever bought it, with proper joinery holding the frame together instead of staples and glue doing the work a tenon should be doing. Watch the doors. If they're hung true and still close with a soft click after a few decades of being opened, that's a maker who cared about the parts nobody photographs.
What separates a cabinet worth keeping from one worth avoiding is mostly in the details you only notice with your hands. Solid wood shelves instead of thin veneered board, because board sags under the weight of a stack of plates within a year. Glass set into a proper rebate, not just puttied in from behind. Hardware that's brass or steel all the way through rather than a thin plated coat that goes patchy the first time a child's hand grabs the pull. A cabinet with real backing boards, shiplapped or tongue and groed, will stay square for a century. One with a sheet of hardboard tacked on will start to rack within a few years of normal use, and you'll feel it when the doors stop lining up.
Age is kind to a well made cabinet in a way it isn't to most furniture. Wood darkens a little, the finish gets a soft sheen where hands have rested on the edge of a shelf for years, and none of that looks wrong, it looks earned. Wipe spills quickly, keep it out of direct sun so one side doesn't fade ahead of the other, and give the wood an occasional feed with a proper wax rather than a silicone spray that sits on top and does nothing for the timber underneath. A cabinet that's moved house twice should show it a little. That's not damage, that's a life.
In a room, a display cabinet wants company that isn't trying too hard, a simple table, plain walls, nothing else competing for the eye once the glass is full of whatever you've chosen to keep behind it. Measure the full width including any handles or feet that stick out, leave a few inches of breathing room on either side so it doesn't look wedged in, and check the ceiling height against the top before you fall in love with something too tall for the room. Depth matters more than people plan for, since a deep cabinet eats a narrow hallway fast.
A good display cabinet is furniture doing the one thing furniture should do, which is hold onto what you care about and get better looking while it does it.