One of the things I tend to hear when people work with some of the game engines out that is that they're "awful." Creation Kit for Skyrim for instance, can be kind of a clunky tool to develop with at times. Trying to cobble together a new space out of pieces of existing places can be frustrating. The main reason for this I believe is that the pieces sometimes feel like they're unnecessarily linked. Instead of having "floor" "wall" and "ceiling" pieces, they're all one static mesh which means they can only be rotated certain ways or it looks weird. Then if you do have a gap then trying to find filler that roughly matches the same style can be frustrating. In addition, with pieces being as specialized as you are you can actually start building an area and then realize that the exact piece you need doesn't exist and now you have to figure out how to fix it. In these ways I can understand how these complaints are valid to a certain extent. Of course, you can always make your own pieces but that also requires quite a bit of prior experience and skills.
So running along the same vain as my previous post (HERE) if you want to be any good as a game developer you will have to accept the fact you will fail... all the time. Not only will you fail, but it will happen at critical moments and you will still be expected to get the work done on time. Since developing a game is a huge team effort, you not getting your work done has a gigantic impact on the rest of the team. So not only will your boss be upset, but the rest of the team won't be thrilled with you either. No one will care that you had issues and thus couldn't get your work done. All of them had issues too but they worked through it and got on with their lives. Failure isn't really a pleasant thing. When I first start in an editor or a game engine there is usually quite a bit of growing pain to be had there. Things that seem like they should be straight forward don't really function the way that they should and worse yet can cause much bigger problems. But there is a lot to be learned from failure.