Most of the major questlines require you to group up at some point, and sometimes multiple times. The elites for these quests are far too powerful to solo, at least for some classes, and grouping up is next to impossible due to the lack of players in the zone. Also, Premade Group is disabled while leveling.
In other words, once you reach a certain point in the zone, you cannot progress any further.
This is the way it’s always been, and it’s why very few people will choose to level through TBC. It’s the worst leveling experience available.
Go back to see Chromie and choose a different expansion, the others are made with Solo Leveling in mind.
FYI Shadowmoon valley was not a leveling zone in Outland. It was the pre-raid gearing zone. Most people were level 70 before they even got to SMV.
I expected Outland to be rough, but I wanted to quest here for the lore. So this is disappointing. I guess I’ll just come back and finish the quests when I hit 50.
Shadowmoon Valley was the final zone for Outlands, so it was designed for characters at or near the level cap. It’s also the oldest content still in the game (Outlands was released in January 2007 so it’s almost 14 years old now), and some of the design decisions they made back then haven’t aged well.