I really like Lumiose city. I guess that's an unpopular opinion, because Lumiose city is apparently very disliked in the community. Still though, its probably my favorite city in the Pokemon world. Here are the reasons: #1. The music. It feels so grand. Like you are exploring a giant city full of grandeur. I remember when I arrived in XY, I was amazed at how huge this city was, since no other city in Pokemon has ever been this huge.
#2: Speaking of the city, Let's talk about the hidden (literally) gem of Lumiose: For those that don't know, Lumiose City has a hidden mechanic called style, which increases as you do activities within the city. It can range from shopping items or participating in battles at restaurants.
Here's a list on Bulbapedia. I think it is a really cool way to encourage the player to go around, exploring the city, and trying all the facilities.
So let's talk about why its disliked: It's way too big and its hard to navigate. That's valid, though I do feel like it is blown out of proportion. There are cabs all over the city and they allow travel city very easily, especially if you have high style points. The other issue might be the fixed camera. When you are in Lumiose, the camera angle changes from bird's eye to first person, and is fixed. This creates a problem when you are navigating the city going downward, as the camera angle is stuck on your face and you can't see where you are going. It is really easy to get lost in that city when you cannot tell where you are going.
I'm guessing those criticisms are why we never had a giant city like Lumiose despite it being very possible on the Switch. Its kind of a shame though, because the only issue I found was that of the camera angle. I still stand that Lumiose is one of the most unique and interesting places in the Pokemon world to explore.