You are 100% correct, but I think the OP is saying many people do just that, do all the little stuff and fail to do the important stuff, no one suggests not to do isolation exercises if you want to, but do the big stuff first as that is what will build your foundation.
Personally I mainly train Bench/Squat/Dead Lift/Press, I have been cutting back on isolation stuff lately, and have found no difference to be honest. I like doing some lat pulldowns, rows, preacher curls and tricep push downs, and thats about it, will change that up soon as well, these are called 'assistance exercises' and are not necessary but nice to add. If I don't feel like doing them I won't and I won't feel bad for it, as I ALWAYS do my main lifts as per my program (5/3/1 in this case). This last week I have had family visiting from interstate and staying over and it's been 37 plus degres in my gym, so I have done almost no assistance this past week, but still completed all my main lifts including some pb's this week as per my training template
For my next training cycle I will be dropping all the above assistance stuff and adding incline leg press, and calf raises as well as more ab work and probably concentrate on body weight stuff like dips, pull ups and push ups as assistance. again if I don't get to them no biggie, life will go on and the important stuff will be done
On the other hand I know a few people that will do nothing but the assistance stuff, and they are not getting any bigger or stronger, as a matter of fact they don't even look like they train at all, one guy in particular recons I am ruining my body by doing squats and dead lifts (he is a PT with his own gym/studio), and he recommends super sets of bicep curls twice a week, yet his arms are 1/2 the size of mine literally, and I hardly do any curls what so ever, may be 3 sets of 8-10 once or twice a week on average will be all my direct bicep work.