thevanishin is spot on though, the EU funds for the project were about to expire and couldn't be allocated to anything else. I'm sure if more time was available and certain circumstances were in place we would have had a dedicated and purpose-built separate facility or at least an extension to the Waterfront that looked better, reality came into play and alas this is the design we have.
Even if the time constraints were influential, I find it hard to believe that no one could have come up with a better design - or at least one which complimented the hall better.
From looking at the plans and images of the current monstrosity, it's clear that
SOME time and thought went into its design. In fact, at one point, concept images of the current monstrosity showed different cladding altogether (which looked better, but still didn't fit in with the hall) and a different window layout (which looked better than the current hodge podge) - so there was obviously time to make amendments and changes.
I'm sure something of similar appearance to the office buildings attached onto the Obel tower would have been fairly easy to plan and design in a short space of time. It might have been boring, but at least it would have blended in a little better with the hall and surrounding buildings.
In reality... it's a poor piece of design and no amount of excuses is going to cover that up.
To be blunt for a moment, I arrange conferences and I've arranged them in other cities such as Copenhagen and Nantes and the organisers nor delegates care what the building looks like externally, what matters is the interior and what the supporting facilities are in terms of audio/visual, spaces, capacity and supplementary meeting/breakout rooms. It's a bonus if the building is pretty, but not many are.
I think you're underestimating the value of building aesthetics (on a skyscraper forum of all places!). If someone has to make a decision on two similar conference facilities at similar prices, then aesthetics are going to play a part.
I know in the past that when looking to rent office premises, I've immediately skipped past some awful looking buildings, solely on the basis that it's not something that would impress potential clients. (A slightly different scenario from choosing a conference venue, I know, but the principles are still the same!)