This was not made by Chris Sawyer (who made the first two RCT games) and that is blatantly obvious as soon as you start up the game. It's a mess. Here are a few reasons why:
Building
Building paths is a chore in this game. Instead of using the old, very intuitive method of picking a starting point and then building from there, they obfuscated the process: now you have a starting point, but the path will try to move in weird directions and you have to interact with the bulky interface way too much; sometimes the correct menu won't even be toggled. And you can't right-click to deselect, so you have to fully close out of more than one menu to select a person after building, for instance. And there's no Ctrl+Z undo anymore, which makes construction even more frustrating.
Music
Waaaayyyy toooo muchhh oofff ittt. You have multiple tracks blaring at you depending on your zoom level (yes, what?), and the noises your customers make are equally annoying and gaudy.
Staff
You can hire as many janitors as you want to patrol your park, but the park still stays incredibly messy unless you want to screw with one of the least fun parts of the game. They've introduced a "laziness" and "discipline" aspect that should be completely optional, but isn't. That means that, even if you have 10+ staff members, you have to check on all of them regularly and make sure they're not getting lazy or that they're paid too little. It takes a LOT away from the game to have to do something as boring as focus on your staff members every ten minutes, because that laziness percentage shoots up fast, even when you don't have your staff members assigned to large areas of your park. Unless you want to deal with this, though, vandalism is rampant and there's puke and trash everywhere (despite there being trash cans everywhere too). And what's the point of benches in this game? The customers hardly use them at all, even when they're eating or sick.
User Interface
This is by far the worst part of the game. The buttons are extremely tiny, and you have to hover over everything to see what things do. The problem is that a lot of the buttons' icons aren't very descriptive, so you end up having to relearn the interface every couple of minutes. It's a disaster; I've never spent so much time trying to navigate through menus inside of menus. Frontier Developments apparently wanted to do everything in a circular pattern to make things pretty, but it's a huge inconvenience; the rectangular menus that RCT1 and RCT2 used were perfect. The window for a ride doesn't even show you the ride's name, and for some reason, in order to pick a person up with the grabber tool, you have to be under the "General" tab. Not intuitive at all.
The sad part of all this is that I was really enjoying the game (being able to create your own guests and ride your own coasters is pretty fun) until these issues added up in a matter of minutes. The biggest one by far? The user interface's size. I have 20/20 vision and I don't even want to bother with it.
If another RCT is made, I dearly hope it's not by Frontier Games.