I suppose it's a bit out there, but there's this open source engine called Godot that supports both 2D and 3D. The documentation isn't great, but it's a powerful engine. It won't have the benefit of being tailor made for adventure games, but you have the option to try and i suppose script those features in.

This is if Unity doesn't appeal to you, which was used for Kentucky Route Zero for example. There's a plugin/toolkit for Unity called Adventure Creator which you could check out as a timesaver: I don't know how widespread it is nor have I used it yet.