Bluntly, getting too hung up on languages is procrastination. Lua is more than fine. (GDScript isn't actually that bad, just completely esoteric). Similarly I wouldn't get hung up on Blueprints or C++ when worrying about Unreal, partly because their C++ is so particular it's extreme.
Defold is basically a pile of interesting simple subsystems, especially around game logic, that in combination become surprisingly powerful, and the experience of the devs shows. It is one of those tools that even if you never use it again some of the ideas stay with you.
