One thing RCT does better than other sim games I've played is having a ton of customization options (Parkitect does this too). I like Timberborn also and wish it would have more customization possibilities like the RCT games. There are some limitations in the RCT games, like setting up a free monorail system doesn't cause anyone to use it to get to the next ride they are heading to, but in terms of decorations there is quite a bit you can do with it.
I only ever had the original one when growing up and did stuff underground a fair bit. One of the early campaign parks came with a bunch of rides and stuff underground off the bat.
I think there were some practical changes to make it a bit easier in RCT2, but it was never hard.