I agree it doesn't look great, but I also think it's worth remembering that this is just a case on the opposite side of the cost vs beauty argument. This was designed by the in house architechture team of a civil engineering consultancy, and the design reflects that, but so does the cost. Almost ever Network Rail project has vastly overrun in both cost and time, yet this station did neither, and that was because it was designed in a cost effective manner, making use of readily available 'prefab' parts. The second you get specialist architects involved, as with HS2 stations, and Brent Cross West even, costs start to skyrocket, not least because with each revision the plans get sent back through the architects, then the civil engineers, and each company will charge a hefty sum for that, especially when specialist parts are involved at the civil stage. By contrast this project was bid for through the Network Rail Framework, and delivery in a cost effective and speedy manner, which is in some ways a refreshing change. This also doesn't mention that the 'prefab' off the shelf parts you see used here are vastly cheaper than custom made pieces of architechture you see in a lot of stations.
At the end of the day it’s a very simple choice of cost vs beauty, and you just can't have both. In this case there was a set budget, and I highly doubt the project would've gone ahead if it would cost more, it likely was a choice of this station, or no station.