There is a lot of stuff sold for the AR.
You have to sort it out by understanding What Range, What Target? Then it should become more obvious what fills a shooters needs.
Taken out of context, one man's major improvement is another garbage junk. I'm no fan of quad rails, but if issued, I'd live with it, obviously because all the different stuff I might also need to clamp on for various missions could be. On my own, I choose plain rifle handguards - because I see no reason to spend $250 on a what constitutes a flashlight or VFG mount. I can't and won't use it on a hunting legal rifle in MO.
That's the point, each gizmo has it's specific place, out of context, it's really bling, totally useless accept as an artistic contribution. This stuff is very much dependent on what you plan to shoot, and how far away.
One major concept most shooters miss is value for the dollar. What do you really get for what you spend? Clamping free float and target trigger on a Bargain Bin gun isn't going to make it suddenly start shooting 1/4 MOA for the $500 spent. It won't be worth the $1099 you have in it. It's still a $600 shooter, with some eyewash bling looks and a feel good trigger. All too many shooters get the cart before the horse, YOU HAVE TO HAVE A 1/4 MOA BARREL ON IT TO SHOOT 1/4 MOA. The other stuff just keeps from taking away from the 1/4 MOA, it doesn't ADD a thing.
Same for ergonomic accessories, if you haven't practiced doubles and can actually shoot two hits in the black under one second, don't expect any trick accessories to help one bit until you can. Again, all too many shooters think owning the parts means they are the dude, when in fact, they ain't. That's like wrapping a black belt on thinking it gives you the skill and experience. Think again.
That's the fallacy of asking any variation of "What's Best?" without staking out exactly what range, what target. What's best for a 600m paper shooter isn't what's best for a 150m running hog shooter, and isn't what's best for a duty trunk gun for an LEO. Some people try to make a case for it, but honestly, it's like saying a Ferrari is the best commuter vehicle during the morning rush. Just maybe a supercharged Mini Cooper could do a better job, eh?
If there's any confusion about whether an accessory will help, then look into who uses it, for what, then reflect on that. Most of it will sort out, even the antirotational pins. If it's not for a full auto lower, then at least they bring a lot of complicated bling to the gun, and some people like that.
Whether someone else agrees, ok, but it's America, we spend money on what we darn well feel like.