Yes, the Sweeney was somewhat rough and ready, full of car chases and non pc language. It was a product of its time and very fondly remembered by a great swathe of British society. Which is perhaps why Life On Mars has been such a huge hit.
And, yes, the Sweeney was a bit of a one trick pony, but frankly who cares. The programme, and its modern successor, were part of a more innocent age, where violence was largely something that happened amongst the criminal fraternity and did not despoil the daily lives of the ordinary people.
John Thaw (a true British Legend) gave Regan substance, and a sort of world weary style which is oft imitated but never quite equalled. It is well worth revisiting.