This is the question often asked on many forums. I do not believe in absolutes so the answer is it depends. If you want to drive on a race track then you need a better handling car. In desert or off-road a good 4x4. Similarly for photography if you are hiking or climbing even an iPhone does a great job. You do not necessarily want to carry a high end digital SLR with an arsenal of lenses on a multi-pitch climb.
Having said that the new generation of cameras have made it possible to use old but good lenses. The following images are made using these cheap but good lenses.