I suppose the raids from the more recent expansions will be available for minimum item level eventually, like Crystal Tower and the War of Magi thing (no clue about Ivalice, I'm already scared of the normal one). But I don't think for the new one that's currently a big issue. Not everyone has done all the normal raids, extremes, farmed plenty of tomestones for radient gear etc. that gives them a big advantage. From 24 people that's maybe the half of it. When we're shortly before 7.0 and we are much further away from the minimum item level (when the equivalent of Ironworks/Shire/Scaevan/Cryptlurker gear is out and plenty of people have their finished relics), the differences will be more noticeable.

That said, it varies a lot of what you miss out and I wonder if the devs aim for things to be less different, when you compare minimum item level vs maximum item level. I've watched a min ILvl run of the Crystal Tower and saw a ton of mechanics that I've never experienced before. Every fight had at least two or three things that seemed "new". When I did a minimum item level run of Void Ark and the Wiping City (I think...?) it was a very different experience, mostly bosses just took longer to beat, mechanics were repeated more and some started to overlap in a way that makes things much harder. (The black circle orb thingies in the geometry fight? Not a big deal with 2 per Alliance, an easy wipe with 5 or so.) It got tougher but not even close to the CT experience in terms of "owo wats dis". It would be interesting for me to see how big of a difference the other raids would make.