One change that seems confusing is that, when you open the main Photos window, you see "Photos" at the top with the most recent pictures and Collections and Albums and stuff at the bottom. So, if you want to see all your pictures, instead of hitting the "Library" button like you used to, now you scroll up, and it says "Library" in the top. NOW you can change the size of the thumbnails! You can make it 5 or 3 or 1 across, just like you could before.
Instead of Recents, you can now change the Library to show pictures in order of Date Captured, as before, or sort by Date Added just like Recents did.

Instead of having two separate views, we have one that can go either way! It's just simpler.
The other great thing about the new system is that there are lots of ways to make it your own. You can eliminate

sections you don't use, and put the ones you want to see at the top. And in some sections, like Pinned, you can choose only the views you like, and rearrange the order to suit you.
I'm still exploring how I can make this all work for me, and it's taking some time. But that's because it has become way more versatile. I'd say, fool with it, and give it a chance…