You can control nearly everything, except the ingredients - the ingredients are natural and will vary from batch to batch. My previous batch of white wine ended up in the bottle with a very light yellow tinge to it, the batch I bottled last week, was colourless and tasted much more refined. Both bought as the same kit, from the same source.
Of course must agree, however early days I tried more water, less water, more sugar, less sugar, and sugar replacements, and seem to remember said use 1 kg sugar and slowly increased to 2 kg and it was too bitter, and had an after taste, so reduced again but then realised the same after taste could also be due to brewing in summer when too hot, which could be got around by using a different yeast, so same bitter after taste can be amount of sugar, temperature, or yeast used.
So the big question, do you brew as a hobby, or to get cheap beer, they are not the same, and as a hobby the more control you have the better, but even large brewers often have the grain grown by independent farmers, and even malted in independent malt houses. It needs a lot of space to malt the grain, as an industrial process you want your beer to have a distinctive repeatable taste so people will buy the beer by its trade name, we all know what Guinness tastes like, but a Stout will vary in taste.
I have considered cheating in a way, when I made prohibition series of drinks the basic method was brew sugar, add charcoal to remove the taste, rack off then add the taste you want to the brew at around 21% ABV, often with a lot of added sugar as well. So you could do the same with beer, make a low ABV brew, then add the alcohol made from sugar after, so the bitter after taste from sugar is removed, but not the wanted taste of the beer.
Commercial they do this by freezing, but under British law this is considered as distilling, so you need a licence, and also needs to be very cold, well below the -18°C of household freezer. But 21% ABV is about the limit for brewing, so you can by blending get a beer to 10% ABV as home brew, but is it worth it? On starting home brew I think every one looks at a high ABV, then one realises we brew so it tastes nice, not to get drunk, so the lower the ABV is the better, as that means the more we can drink before falling over, so around 3% ABV means high enough so it keeps, and low enough to drink as a session beer.
I love Morrisons own Bitter around 2% as can have a BBQ and drink the stuff all night without falling over, but with Carlsburg Elephant or Porta you don't drink much before you throw a track.
So I home brew for cheap beer now, bag of sugar and can of concentrate and cover keeping at 20°C for 3 weeks or more, then bottle in old pop bottles so easy to bottle and you can test without opening if pressure is OK. i.e. keep it simple.