You may not have magically popped up from nowhere but the aircraft that departs from a considerably closer aerodrome did. Giving delays a long way out (as per ALOFT into SY) works well when the arrivals are well known and orderly but once things get busy and less orderly it becomes harder to manage.
Wouldn't these be RPT with a known schedule.
In the end, yes your magic box can work miracles, unfortunately the magic makes no allowance for the other 53 aircraft doing their own thing too. You're just as likely to run up the @rse of the guy ahead because you chose to lose the time on descent and he was doing it in the cruise. Until all that can be coordinated it's down to a decidedly basic box of tricks called me!
It could work miracles if it were allowed to. RTA + - 5 seconds, efficient descents, the whole bit. Why would the 52 other RNAV equiped aircraft be 'doing their own thing'?
Unfortunately, like me it doesn't like normal descent + now min speed descent + holding + vectors + re-intercept star + max speed to the field + track shortening + cancel height rqmt + cancel speed restriction + on second thoughts slow back down to min speed; all in the one descent.
The idea of 52 other aircraft crews having this sort of schizophrenic workload at the same time, at the same place is just scary.