I never thought picking out sights for my AR15 would be so hard until I put optics on it.  I started out with a Bushmaster XM15E2 a few decades ago and that was the simplest design.  You had two aperture sights for close up or long distance shots.   The carry hand design would allow you to put an ACOG or other optic on it but this was not a popular way to do this.  Flat tops became more and more popular in the industry because optics became rugged  and durable and even though shooting with iron sights takes great skill, using them as  primary sights, especially in the military makes you limit your firearms abilities.

Many optics are used for identify targets as much as they are for hitting then.  You do have to be careful about what type of sights  you want to put on your firearm because Troy Battle sights are very popular but there are big differences in clearance for fold down front and rear sights.  Gas block mounted sights are lower and if you get fixed sights, you won’t be able to mount magnifiers behind something like and Eotech.  I’ve got iron sights sitting in my house that got about a year of range use and then I picked up a new  optic and the configuration just didn’t work.  The best thing to do is think ahead or just plan on having more than one upper for your AR15 and configure them differently.