I can't tell what you are describing -- are these McMansions (which tend to have random useless rooms that make no sense) or traditional 1940s colonials (which often have a traditional living room with a porch/sun room off of it).

I'm a little confused. Do you have a living room, dining room and family room?

Pocket door and make it an office

What do you need, OP? do you need a spare office or playroom area? It can make a nice library or formal dining room or music room.

Reading room. My parents have one and it's a cozy after dinner "drawing" room.

This is a pretty traditional set up? Would just Pinterest.

Add a glass door so you can have an office or something in there.

We have this exact set-up. We have the TV and piano in there. In our big family room to the rear of the house, we have a sectional that faces the kitchen, and no TV.

Prior owners used the front living room as an office. Our neighbors have it furnished as a library with big shelves. I thought we could use it as a guest room in a pinch (with screens across the doorways) but have not tried that.

I have two living spaces- one clean adult space (piano, books, comfy chairs, fireplace) and a family room with the couch, tv and toys. I love walking into the house and seeing the clean adult space first. And I can entertain there while daughter is in family room.

OP here. Sorry that I wasn't clear. There is a foyer, but right to the left or right of the foyer is often this open room that has only two walls.

And each opening is super wide, so it's hard to imagine that any doors could fit that space.

We added doors and made it an office

Add French doors and make it into an office.

Library with a bat cart.

Piano with a couple chairs.

Google how to create a foyer. You should get some ideas - half walls etc.

It is my pet peeve when the front door opens to the living space. There are ways to create entry ways.

In a lot of houses that we're looking at there is a living room right to the left or right of the foyer, and in most cases there is no door plus it is open to another room right next to it. In our home countries we didn't really have this feature, so to us this is kind of a wasted space.

We do not want to use it as an extra living space because we only need one family room. Does anybody have any creative suggestions for how this room can be used? And maybe it can be closed off?