Most of the open-plane area looks plain and samey. I couldn't distinguish one end of it from the other. Yes the Venice-esque city is very pretty but so far we've seen very little from it other than a couple of streets maybe, the inside of one building and a "lake".
If the table-scraps of variety they've shown so far satisfies you then by all means get excited. But other than the scale and modelling/animation of what they've shown so far, they've shown nothing that has gotten me immensely interested.
Compared to most previous FF games, the "variety" they've shown so far is underwhelming in my opinion. If you disagree, we'll just have to agree that you disagree but I'm not going to excuse myself for doubting Square Enix after what they pulled off with FFXIII which went through similar development woes.
If you want to see a trailer for a AAA jRPG that shows off proper environment variety look at the Xenoblade Chronicles X trailer. I'm not going to praise and make excuses for a game that has been 9 years in development and the director for the game can't answer a simple question of how big the landscape of the game is going to be, and that's because the honest answer probably is: "It's going to be as big as we can make it until Squenix pulls the plug and needs some quick cash inflow. The rest of the unfinished content will be recycled and reused for the sequels." just like XIII was. THAT is my "jump to conclusions" opinion, everything else you suggested is purely anecdotal.
When Monolith Soft's president was asked how large the world would be, he gave a straight answer which was translated to:
I don't want to sound like I'm just tooting Xenoblade's horn, but so far they've hit all the right marks with all of the questions and ways they've shown and shared info about their game and Square Enix has done almost the opposite for the longest period of time in which XV has been in development.
If your idea of variety is a cave, a plane, a plane with some trees sprinkled, a plane with a lake in the middle and a gas station I don't know what I can say to contradict you. I honestly think FFXV is going to be a very wide and open corridor with a lot of padding until you reach its abrupt end.
You and I and all of us have been looking at exactly one region of FFXV, that is Duscae region so far, and there is many other more, and we did not even see the entirety of what it has to offer. Why is it such a surprise that one region looks mostly similar from one end to the another? And your complaint that it looks plain, well fucking duh, it's still in development and it's also considered a beginning area of the game. In the Paris game show walkthrough footage, it was explicitly stated at the start of the video that enemy and event were removed for the demonstration as it was to show the scale, and that different exciting elements will be included in the actual product.
Now, realistically speaking, no, of course this game wouldn't be close to what Xenoblade could offer in terms of environment varieties-ness and fantastical element, but does every open world now should just do exactly what Xenoblade did? Can't FFXV do its own thing, establishing a fantasy world that is still contemporary at its core, and more grounded by reality? Games like FFXII, Shadow of the Colossus, Dragon's Dogma and Morrowind can get by with mostly large, barren open world with relatively flat land design with nowhere near the kind of overworld design Xenoblade had, but people found them to be enjoyable. Because these games aren't ALL just about the world map and exploration. I guess you want FFXV to do the same thing as Xenoblade and fill the world with collectibles and fetch quests as well? But that falls into the idea of padding, so what do I know. Or are you wishing for a Xenoblade clone? Like, let's forget being original, let's just do precisely what another developer did and call it a day. Right?
People need to realize this game is still at least 1 year away for pure development, they simply aren't going to show
everything to you when things could change as the development progresses right away. But that's where the demo is going to come in. If you're not getting Type-0 HD, watch other people's impression, let's play or whatever and judge for yourself. And if you're playing the demo, provide feedback if you truly wants the game to be as good as it can be.