Open concept is great for staying a part of the action in adjacent room while in the kitchen. The down side to those 2 rooms being open is that watching TV while someone is running water or cooking food etc can be distracting. Also you have to figure out how to hide your mess if you have company while you are preparing to serve.
Regarding the other rooms in the house. When they open to one another, you lose walls for hanging art or trying to place furniture. If you have larger pieces of art they have to be rotated in and out of a closet to be displayed. ( which can be like getting new ) When you factor in windows, tray ceilings, fireplaces and other "obstructions" it become challenging to even place basic furniture. This is apparently a huge issue for so many people who post design dilemmas for those very reasons.
The other challenge is adding color to walls. Where do you start or stop a color? Sometimes it can be confusing when the wall just keeps going and turning a corner, but all in one room. As well, different flooring types that dictate where the "room" is can be an issue, whereas all one type of flooring allows you to extend your spaces. I would not be driven to purchase or not another open concept floor plan, without considering all the other factors of the home first.

Open concepts work great for families with small children so the parents could keep an eye of them while in the kitchen. Most people who entertain guests tend to gather around the kitchen area for the majority of the time. The key is to provide adequate storage in the kitchen so the 'mess' is hidden or easily stored away.

It is also more practical in addition to the open living areas to have a separate, private 'flex room' so it could be used as an office or study.

I can totally block my kitchen off if I choose to. I have a door at the stariway for upstairs & I also have a swinging door into the dining room. For the most part, my kitchen cannot be seen from the living room.

I've never liked to see small children around kitchens - too many hazards - and the cooking smells (and noises) tend to spread around the house more quickly. Personally I much prefer separate rooms.

More and more homebuyers are requesting "open plan" homes

I've voted 'don't like' but it depends on lifestyle. I like that it keeps family in touch with each other, even if the cook is only watching the TV and watching the family watch the TV. Good, too, for casual entertaining to a degree. For me, my living room is a haven. I don't even want to think about doing the dishes.

I know open concept is a must for many people in my demographic - young families with kids - but it's never been a must for me. Maybe because I love old homes and they tend to have a more separate kitchen. In our recent remodel we chose to keep our galley style and extend to the backyard and chose not to bring down any walls to open to the dining area. I sometimes find open floor plans to be more of a hassle with small kids because there is no way to barricade access to certain areas. I also like the idea of the kitchen not being on display.

I also like my "closed" kitchen to barricade the dog when needed.

i like them to a point.

i like having wide enough doorways that other rooms are easily seen, but i like having the walls.

i also have tons of art, so i like being able to display it.