A linear storyline does not equal 'depth'. I haven't seen the kind of 'deep' game you seem to describe.
I like that ED doesn't copy what all other games do (because other games are played through in a couple of hours and then forgotten.). Some people need to be told how to have fun. Some just don't - they find fun in stuff like ED all by themselves. Which is arguably the better type of fun (because it's your type of fun and not you trying to adapt to someone else's idea of what fun is.)
You played through skyrim in a couple of hours ? Any Bethesda game has depth (not the MMO part - that was a predictable fiasco)... and there are 'let's play' videos on you tube of the same guy adventuring with the same character for the best part of 6 months...
Those worlds live... they are modded to add ever increasing content by the faithful community.
You also can totally play skyrim for hours without ever following the main storyline arch... I have done that on at least 2 playthroughs and had the best fun doing so. No scripted missions... just wandering their world and exploring and facing the elements...
And do not tell me FD is a small company. It is the role of management to set goals commensurate with the size of their resources. Of course when you received an award from a queen for developing a game it might go to your head just a tad bit and you forever want to surpass what you did before, even if, you clearly don't have the resources required...