>> UX research and (more importantly) user expectations continue to evolve.
The beta has RESOUNDINGLY failed to meet the expectations of the current user base. Surely you mean "the user expectations of our new target audience are different to the current user base". Y'know, as in, "we don't give a crap what the current user base thinks, we want THAT user base", which of course begs the question, if you're not interested in targeting the current user base and want to target another i.e. target a more mainstream audience, why not start an entirely NEW website targeting that audience, rather than trash the current community in order to do that?
>> The classic design in 2014? Not too bad. The classic design in 2018? Probably not going to cut it.
It appears you have a crystal ball that predicts the future. Tell me, what exactly happens in 2018 that stops the current slashdot design from being a poor fit for the problem it solves?