I am guessing here, but it seems plausible.
On tracing your quest completion for Waking Shores, https://www.wowhead.com/quest-completion-tracker#eu-argent-dawn-luciferkain I see you have actually done the quest Dragonriding, and Skytop, but skipped the other Dragonriding and some of the following quests https://www.wowhead.com/quest=68795/dragonriding#comments:id=5481469
You have done https://www.wowhead.com/quest=68799/return-to-the-ruby-lifeshrine and Training Wings (become the ltiile dragon whelp and kill plants on the inside of the tower) but not
and the next quest
These are needed to progress the Waking Shores storyline.
Now, either you just missed Who Brought the Ruckus, or it depends on having done one of the Dragonriding quests you skipped.
Either way, I’m thinking that’s why future quests have dried up - because you have to complete those.
So, check out Who Brought the Ruckus. If it definitely isn’t there for you, you will have to get back on the quest chain somehow.
If the Dragonriding is the problem, I have a couple of Horde characters that could join you to go through them.
I know that I can carry someone through getting the Dragon Glyphs, because I’ve done it. You click the green arrow when in party, and turn into a whelp who tags along behind. I’m guessing then that you could also do this for the other Dragonriding quests as well.
If you want to try this, let me know, and we’ll give it a shot.
Once you get past the Dragonriding introduction sequence, you don’t actually need Dragonriding much (or at all) through the rest of the chain. It’s a fast way to travel, but as far as I can see, every required quest is accessible without it.
So once you get past this block, you should be good to go.
P.S. Don’t write off Dragonriding entirely just because you can’t do the racing stuff. Hitting Skyward Ascent a couple of times and gliding gently will get you up to a high place and can cover quite a lot of ground, so you can do that much perfectly well.