There's nothing wrong with knowing a lot of knots... but they have to be practiced to be remembered on demand, and if you tie a knot wrong at the wrong time you can really fuck your whole day up.
In the climbing world, we've really been using less and less knots. The bowline is all but abandoned, with the figure-8 being easier to remember, verify, dress, and is overall more secure (the ONLY advantage to a bowline over a figate is that it's easier to untie after loading).
Knots I regularly use and would recommend anyone know:
Figure 8 in it's several varieties (on a bight, follow through, bend)
Square knot (not what most people think it is)
Alpine butterfly
Clove hitch
A trucker's hitch is also a great one to know, if you find yourself lashing a lot of stuff. If you don't, it's just wasted neural pathways, like all these other crazy knots you'll never actually use in the field.
Also, understand the difference between a knot, bend, and hitch. It probably won't save your life, but there's value in knowing and using correct nomenclature.