I was actually pretty apprehensive about the game not being open world. My two big concerns were that it would be targeted to smaller children (like Let's Go) and that it wasn't open world.Ohh okay! I thought there might be something like a free mode, where you can walk around and just take pictures like that.
I've never played the original, so I had no idea that it was always like that. Thanks for clarifying!
I haven't regretted it at all. I think you could do an open world, but that would make it a different game. Each time you take the same trail, you can see Pokemon doing different things, in different positions, you can do a few different things to try and interact with them or get their attention, and overall, I found I wasn't happy to do the same trail only one or two times. That's been my experience anyway.
Edit: You also get a little page where you can display your favourite snaps online, and people can view them. Surprisingly I've been enjoying editing the snaps and choosing my favourites for my space.