All of the above is true. Except for the part about arms. The guys that say my tris get enough work from training chest/shoulders or the guys that say their bi's get enough from back are full of shit. If you are genetically gifted the most you can get away with is not training smaller bodyparts such as forearms, traps, calves, and abs. But thats the very very few and fortunate.

Lagging arms can quite easily be fixed with weighted dips and weighted chinups/pullups. Neither of which are isolation, and which you should probably be doing anyway. Regardless, biceps will get decent development from rows (particularly if done underhanded) and triceps will get great development from bench/OHP.

These guys want the buff appearance i think, body builder style so machines and biceps curls and all that are ok. Its just that they should know that the muscles will mean nothing except eye candy.

I agree with the overall sentiment on this, but I think getting more nutrients while it may not be very important in your muscle building will be beneficial in overall well-being and longevity. They also become far more important as you get older and muscle mass retention becomes harder without iron and vitamin c.

exercises like dips and close grip bench are useful for building tri's, but underhand rows will not build biceps unless it suits your structure and even then its still shouldnt be a staple in a biceps routine. I've been doing underhand rows for years and its built me a great back but my bi's still suck.

Size and strength are not the same, but they're very, very closely related. It's not like you see powerlifters squatting 350kg with chicken legs, nor do you see bodybuilders benching less than 100kg for a max. Everything I said still applies to bodybuilding up to a point. Of course, those looking to compete or work in the field professionally will need supplements, more isolation, etc. However, for the typical user on this forum, who just wants a decently muscled body and a six-pack, my advice holds true. Supplements/machines/etc are tweaks to a fitness regime, not the basis.

tl;dr: No, everything I said still applies to someone who just wants to look good.
Nutrients are very important for health, yes, which is part of the reason why eating food is so much better than taking a protein shake. Generally, protein powders and supplements have minimal, if any micronutrients in them, and the macronutrients (protein/carbs) are of inferior quality to those you can get just from eating meat, fruit, veg, etc. Notice I was just talking about macronutrients.
I would hazard a guess that you're not rowing enough weight. I did nothing for biceps but rows for half a year from the point I started training, and still got great growth. Right now, all I do for biceps is rows and chinups, and I still have bigger biceps than my mates who seemingly train arms 3x a week and only talk about how much each of them can curl.

Its a structural thing. Not every exercise or technique is going to build the same mass in every person. We all have different length tendons ligaments, muscle insertions and attachments. Every single person on the planet has a unique musculature. We all have the same bones and muscle groups but they arent all built the same way. Some people feel underhand rows in their arms, I dont at all.