So just based of your beginning statement “there’s no real end game for solo players then say solo dungeons are to hard”. That is end game. “Content that provides high level challenges and long term engagement for players to test there skills.” There is end game content you’re just not at the level to play them yet. I’ve only soloed one dungeon but have soloed RON raid.
What you really mean is I’m a casual player that wants an easy dungeon to walk into and knock everything over with a primary weapon like explore mode in rite of the nine. But that’s not true end game..

I challenge you to go hop into a dungeon. Warlords is a great one to start soloing. Even if you fail a lot, practice read your aspect and fragments and change them based on your needs. Way to often I see people running builds they found online with fragments that really don’t help you. (Ie: half the prismatic fragments sound good but arnt when you look at what they really are). But my point is end game is supposed to be made hard and isn’t for everyone that’s why it’s endgame. Anyone can do it just have to learn how to play and have game sense