As someone who has done loads of dungeons, loads of fractals, and a few raids, I would like to make a suggestion for how to branch the gap.
Here are my main thoughts on WHY before I mention the suggestion.
1 - Dungeons were a good idea having story with content, but that content is now very easy for basically everyone ( and won't ever be updated cough AC trap chains cough ) and having it be easy enough for 1 player (in the right gear) to do solo is fine.
2 - Fractals then added sort of "end-level" dungeons that are easy at first and get harder as you scale up (eventually requiring full builds etc. to even attempt it)
3 - Raids were then added with HoT which was a "nice" thing at the start but now I think it's divided the community a lot, those that raid constantly, and those that basically never raid.
I am a PvE player and thus - I do not pvp nor wvw, and as I also do not raid anymore, there is 0% chance to get legendary armour ( which is very expensive and I'll probably never get anyway). HOWEVER, I love learning about story and lore and the fights and mechanics etc. of the raids.
So I have a simple suggestion that is so simple people will hate the idea.
Add an Easy mode ( 5-man) for raids, effectively turning them into dungeons, Make it so 5-man cannot get any of the ascended drops, and can only get one legendary insight per raid ( not per boss) per week. This way, People such as myself who don't raid due to (in my own opinion) an elitist sub-community, get to experience the story, the art and the boss-fights designed, albeit easier. So I can then enter a raid with my group of friends ( coincidentally there's a total of 5 of us : D ) and complete it getting the story I love to read and the fights I wish I could do if the community didn't want specific builds for specific sections with specific gear that i(n one case didn't let me raid due to having the wrong runes on my character, right stats and trinkets, but I had 2 trapper 4 nightmare instead of 6 thorns - do not take this as me being salty it's anecdotal evidence, do with it what you will) prevent normal players experiencing it ever.
It came to my attention with the newest raid - Hall of Chains.
As far as I understand - it is basically the underworld and you must fight the end boss who was a character from GW1. A Friend of mine has successfully beaten this raid already, but that is because they have a team full of competent people with the correct gear, while I will most likely never experience this raid, I would like to have enjoyed the story in it, as there are a few intractable objects in the second wing (maybe) of the first raid that changes depending on if you are an Asura or if you're a Necromancer etc. Hiding these bits behind hard content that is "too hard" for normal people is in my opinion, a bit unfair, They can keep their legendary armour etc., but I feel that the story should be freely experienced by everyone.
TL;DR: Add an Easy mode to raids that removes some(maybe all) of the current drops, set it at 5 man party (not squad) so that normal people can experience the story atmosphere and fights.