New brewers should concentrate on cleaning and sanitation, mastering yeast management, fermentation control on the way to make good beer. Water chemistry adjustments then can be applied to make excellent beer.
This is good advice, but it is not a mantra for all.
IMO; as a starting point, you have to have water that when mashed with the grist will give you an acceptable mash pH. The tinkering with the detail and fine tuning of mash pH comes a bit further down the line once more understanding is gained.
I am a lover of pale ales (both English and American)....when I started brewing all grain, for the first year or so I had to tip batch after batch and I could not understand why.
I used campden, used tried and tested recipes, my technique, yeast handling and sanitation were all sound.....yet I could not produce beer that was acceptable. In truth, I almost gave up.
It took me a long time to understand that my favoured grists and an alkalinity of 120-130ppm just don't work. Now, had I been brewing stouts my experience would have been a whole lot better.
What I'm saying is that there are certain combinations of water type and malt that will not turn out well. A new brewer should understand this and be aware that it might not be their technique or sanitation that is letting them down.