Honestly, I’d guess that most fields have a ton of employees that don’t know what they’re doing in them, it’s just much more apparent in this one because of the clear and drastic negative effects that occur when their bad advice is taken.How come everyone in this hobby has accepted that many LFS have employees that don’t know what they are doing when we wouldn’t accept that in any other aspect of life. Don’t get me wrong I have accepted that too and do my own research before going into the store but if this were any other part of our lives we would be just as furious as op in the same exact situation
For example, it's obvious someone is giving bad advice when they tell you to put a shark in a 20 gallon tank (especially with other fish), but it's a lot less obvious when someone is giving advice for things like grow lights by saying "go with the higher wattage light, it'll be more powerful," even though it's not necessarily true (in fact, I know of one LED company that markets two lights with the exact same specs, but one is 600 W and the other is 1000 W; they admit that there is literally no other difference between the two lights [they have the same PAR and spectrum and everything], so going with the "more powerful" 1000 W literally just raises your electric bill with no benefits over the 600 W).
To put this concept into other terms, I know it's a bit of a running joke in the corporate world that most bosses have no idea what they're doing (I've personally had some good bosses, some mediocre bosses, and a couple of terrible bosses - I'd imagine most people are in that same boat), and my family in programming all talk regularly about how they have to come in and correct shoddy work done by other programmers who clearly didn't know what they doing.
So, again, I think it's generally expected that some employees just don't know what they're doing (and some likely never will) no matter what field they're in, it's just a lot more obvious to the public which employees are the bad ones with fields like this hobby.
In closing, as I like to joke with my wife, "Fifty percent of all doctor's graduated in the bottom of their class." No matter what field you look at, there will be some people who are really good at it, some who are really bad at it, and a lot of people in between at varying levels of good or bad - it's really just a matter of figuring out who is where on that spectrum and listening the good ones (which is sometimes easier said than done).