The Dreadnought was designed as a stablemate for the Constitution class , to be so frightening as to make war unthinkable.
These ships were constructed until 2275 when design work began on the Excelsior. As combat ships they are superbly effective, and were very successful. The Klingon Empire struggled to keep up with the firepower and effectiveness of this ship type.
The Dreadnoughts were so expensive to build, for their day, that each was a special project. Almost no two Dreadnoughts came off the ways the same as her sisters.
But they were expensive to produce and run. They had huge crews and mainly stayed near Starbases awaiting the infrequent call to battle.
Several Dreadnoughts were refit into super-cruisers. While still expensive to maintain and run, they were nicely effective at confronting problems.ready reserve where they aged out.
The super-cruisers were used until the cost of refitting them became just too great and they were retired, usually to be scraped out.
Two remain as museum exhibits. The Original USS Federation, the flagship of the fleet and used as presidential transport for everal years, and the USS Alliance, a super-cruiser that became popular and is now on display.
Some opine that the modern Sovereign class is analgous to a Dreadnough, however this is more true if the ship is compared to the Super-Cruiser mode of the Dreadnoughts.