Many photogs will buy a really expensive camera then top it off with a low-budget lens to save money which is dumb. Always invest in quality glass.
Nobody's trying to say that, up to a point, putting money into buying a good quality camera is not important, it is. This is however only part of the equation in terms of producing quality pictures and probably the smaller part too.
More important is glass, as without this your camera is just a pointless piece of junk. You need glass to make images and the better the quality of that glass then the better the quality of those images.
High quality glass won't make you a better photographer but it will ensure that you get the best possible technical image quality out that expensive high tech new camera of yours and in turn help you realise your investment rather than ruin it.
So some thoughts of the why's and wherefores. As we have already implied poor quality glass adversely effects the quality of your images, no matter how good your camera. Also the build quality of a lens made with cheap glass usually reflects that economy, the whole thing being built to a price.
This brings us to another point, quality glass being normally mounted into a lens of excellent build quality that not only lasts longer but retains high resale value too. Most quality lenses will outlast the many camera bodies we buy over a lifetime, which regularly come and go, and indeed will outlast us if well cared for.
Then there is the question of false economy. Many of us end up buying the same lens twice so to speak. The cheaper one first, convincing ourselves it will do, then the one we really wanted sometime thereafter having been sorely disappointed with the make do one.
Better to have the patience to wait until you can afford the lens you really wanted in the first place than fork out twice and be stuck with trying to sell off the first, lesser lens with a poor resale value to boot.
Thus quality glass is a sound investment both in terms of image quality, longevity and economics - always buy the best you can afford is a good maxim.