Daleks - Metal boxes. Yes, there are subtleties in designs, but in the vast majority of cases individuality is specifically bred out of them. All just 'Daleks.'
In the new series, yes. With the exception of the obvious leaders like the Emperor, or Davros, or the Supreme, or Cult of Skaro, or the Paradigm Daleks, they're an army of foot soldiers so they have to be identical. It's cheaper to reuse and refurbish old props than create new ones for each serial.
Go back to the original series though and once you get to the colour serials they started to change them slightly every story, so they did appear different each time you saw them.
That said, Doctor Who has always been held back by budget. I'm sure they'd love to do different types of alien species each week but it all comes down to money.