Road tool, LPV, the Kite Demo for eg and Epics games are also hardly indoors, things like outdoor lodding used in Paragon. There are alot of tools that are simple not needed for smaller games but Open World is a popular buzz term so it makes sense Epic went along with it for marketing but the realities of the genre are far less optimistic. The Witcher 3 and Breath of the Wild being exceptions.
My point is they rushed to support people making open world games because everyone was jumping up and down (to repeat myself for the 3rd time btw) and implemented the tools in a fashion that was not largely beneficial for everyone and actually detrimental in the damage it caused to the stability of the codebase.
I cant honestly do this because the engines I know with the better feature sets for open world games are all in house, Snowdrop, Frostbite 3… Decima and there are more but Epic is actually an oddity in the industry not the rule. The issue for me is largely that bleeding edge graphics do not represent the games industry at large and those that need that level tend to have inhouse engine teams (even if they are using UE4) so I would much prefer to see the focus on features which help to make better games with the engine because its clear thats where the competitive advantage is atm not graphics 
I just think the world could do with a few less clones and a for more large ambitious games that arnt simply a string of buzzwords tied together! Game projects die every day even for the biggest badarsed studios on the planet.