While you can buy commercial brands, they are not any easier/harder than dry ferts, and you are paying for 99% water, and quite a pretty penny for that water
You still need to read and follow instructions on any commercial brand and figure out the rates and how much to dose.
This is no different using a dry generic powder vs a commercial liquid.
Except cost really.
KNO3 cost about 3$ per lb
One little bottle of say Pfertz is 15$
I dose 1 teaspoon per day(5 grams or 1 teaspoon) to my 180 gal.
How much Pfertz would I require and how long might it last to add the same NO3?
I'm guessing at best, 45 days.
2X as long for assuming that their dosing is the same as the 5 grams in a 180 of KNO3.
So that is 10X cheaper, and just as easy to add.
Shipping dry concentrated ferts is much cheaper than liquids.
Plus, such basic nutrient estimations, and consistent nutrient use vs a wide range of commnerical productrs with different concentrations does not help later on if you compare with other folks that use the basic salts like KNO3, KH2PO4, GH booster, Traces.
This helps folks to be all on the same page.
You only add 4 things, after you read a bit, figure out how big your tank is, how much to dose via table, or a dosing calculator etc, after that, it's old hat. Same is true for any commercial brand.
Simply ask how much to dose.
Folks will tell you.
Plenty of sites discuss it.
This was the whole thing on the web a decade ago using PMDD methods and DIY ferts. They are no harder and the cost is virtually nil after you buy a few pounds of dry bulk ferts, you will not buy any more for a years typically.
That's the point.
This is why/how a little knowledge can save you time, $ and work/labor.
There's long discussions about PMDD about the differences and reasoning about DIY vs Commercial brands.
Do not be put off and weird out by Chemical formulas, you still add those no matter what brand or DIY formula you pick. You only need to know 4 basic things/names. You can use teaspoons. Pretty easy.