No. You Git Gud by actually playing the game and practicing until things like muscle memory start to kick in. THis is not the matrix where just randomly filling someones head with book knowledge makes tehm a kung fu master. Just like you don´t become a F1 Pro by never driving a car or get good at basketball by watching the NBA on TV.
If for example you´re LoSing yourself on Shriekwing 5 seconds before the roar pops, those are 5 seconds where you could have been doing damage but were instead just useless healbait. If you´re too busy dealing with the wrest mechanic to do damage on Ansurek, you need to practice basic gameplay, and no amouot of % improvement from BiS gear will save your performance when you´re shafting yourself out of 50% my being out of position and having to run after a boss even though you knew beforehand where it was going to be pulled to… You can read /watch as many guides as you want, until you get the practical knexpereince it´s useless… teh RBMK reactor at Chernobyl was also theoretically 100% explosion proof… Now, how did that work out in actual practice again? 
And until that practical knowledge and experience exists, everything else including BiS lists and Bis Talent builds is effectively just attempting to build a ladder out of crutches. Instead of slowly building your way into a class by leveling and taking mostly passive talents, only adding more buttons when you understand the ones you already have, people buy a levelboost, copy the “bis” talents, and are then so overwhelmed by a dozen buttons suddenly being in their bars that they fail at the basics by trying at all costs to be more advanced than they actually are. 
Calling this a “time sink” is IMO highly debateable at best and laughably irrational at worst. A “time sink” would be mora along the lines of not allowing alts to skip the intro questline, or requiring you to spend hours doing all the siren isle quests again to get a second one… not providing a 15 second solution to any percievable socketing combination.
They´re actually effictively preventing it from becoming a time sink by allowing alts to skip and allowing easy resocketing, instead of having to redo the Command table quests to reacquire gems that were destroyed by resocketing. THAT would be a time sink, not click, drag, click, drag, click, drag, done. 
Yes and no. They´re not “Wrong” per se, they merely assume a level of both gear and skill that most players will never reach, which in turn makes some of the choices bad in practice for most players. They also assume a well coordinated and properly raidbuffed group setting, and not a random PuG that can´t even be arsed to even get on discord to coordinate kicks, and are also primarily aimed at mythic raiders not Keypushers, though they do touch on that aspect in most of them.
But at least they are also explicit about stating the first part with regards to the BiS lists on class guides, wheras many other guides make other equally flawed assumptions that may or may not be applicable to the player reading them, but don’t mention any caveats but present themselves as the end of all knowledge, so people that don´t do their own research treat them as gospel instead… Essentially both apples are poisoned, just with a different toxin, which is why so many that actually know what they´re doing recommend simming your char and keeping your sims current instead of blindly following a BiS guide that´s only relevant for the top 1% if you`res only running LFR/N/HC.
But most people unforunately don´t care either way an just eat whatever poisoned apple they get served because streamer X and /or semi-famous pro Y told them to…and if you´re not thinking for yourself, you have no reason to wonder why some decisions were bad. 