That shows that Starfleet evolves, and comes up with more advanced ships, while the Klingons simply construct the same ships over and over again. If Starfleet evolves and the Klingons don't , how can it possibly be defeated?
The Klingons did construct ships besides the BOPS (of which there are at least several variants and sizes), though, namely the Vor'cha
-class and the Negh'Var
-class. So their tech is not as static as that. They may have an overall tech disadvantage compared to starfleet (IE replicators, creature comforts, etc) but when it comes to weapons and speed, and cloaks (where it really counts for war), I think the edge belongs to the Klingons.
Unlike Starfleet ships, these are constructed to be completely built for war, whereas the Starfleet counterparts are multi-role, primarily built for peace keeping and exploration. Not to mention, the Klingons do have cloaks. I would hate to see what would happen to an unsuspecting Galaxy class or Sovereign class ship when a cloaked Negh'Var
-class goes in for the kill! And let's not forget the BOPS aren't push overs, either. In the Defector, 3 BOPS (plus E-D)were enough to scare off 3 Romulan Warbirds. In fact, if you ask me, the Romulans must have had enough respect for the Klingon Bird of Prey design, so as to borrow heavily from their design, when they created the Valdore-type War Birds from Nemesis!
Just because they don't change their designs as much as starfleet doesn't indicate Klingon ships are less powerful. In fact, I would argue that the reason starfleet ships change in design so much more is that they were evolving from exploration\peace keeping, to all out war ships. Basically, the UFP was gradually changing designs and seeing what works and what doesn't, thus the constant upgrades and evolving designs. The Klingons didn't need to evolve because they were already on a wartime footing.