This kind of argument has been made since the days of renderware.
I have seen a number of projects go from
'We're building our own engine'
To
'we should have just gone with $engine_of_the_day'
To
'We were so lucky we chose to make our own engine'
If you want to make a game like fortnight, the Unreal is your pick. If you want to try something that hasn't been done before you could do worse than rolling your own engine.
Especially if you are looking for where the fun is, the idiosyncrasies of your own engine gives you a world with it's own flavour if you incorporate that flavour into your design process you could create a feedback loop that turns into something special.
I have seen a number of projects go from
'We're building our own engine'
To
'we should have just gone with $engine_of_the_day'
To
'We were so lucky we chose to make our own engine'
If you want to make a game like fortnight, the Unreal is your pick. If you want to try something that hasn't been done before you could do worse than rolling your own engine.
Especially if you are looking for where the fun is, the idiosyncrasies of your own engine gives you a world with it's own flavour if you incorporate that flavour into your design process you could create a feedback loop that turns into something special.