At the time, Suramar’s dungeons were Heroic minimum, in other words, they would have to be reworked to have a Normal version of them. Since they were Heroic as a minimum, then one couldn’t tackle them before one had spent time gearing or had a friendly group to carry them (which is impossible if you’re one of the first to hit them).
Admittedly, the story only called for tackling them after a month’s time-gating (at minimum), so one MIGHT be ready to tackle Heroic dungeons by the time the story called on it, but if one was just running straight through, the first ones in to a Heroic minimum dungeon may be forced to hold off till gear would let them handle it.
That would almost be going back to Vanilla or TBC way of time gating, but I still think we’d see patch burn out happen too fast to justify to the money crunchers.
Edit: On the other hand, the gearing rate is one problem. At this point, I honestly think the game would be best to keep characters at level 60, and use storyline unlocks for improved gear, much like how Renown was used to gate WQ gearing, but this time link it directly to the story.
In Threads of Fate, this would be based on tiers of progression in areas, such as at 50% in your first zone’s completion, the iLevel progresses to 120, and when you complete the zone’s progress, the rewards you get are now set to 125.
Well, in Legion, if you were leveling an alt, once they were in Suramar, they would complete a time gate, and then be done with Suramar for the week in terms of story. It became better in Suramar once the BfA pre-patch hit because you could burn through it.
I’ve completed a max-level character through the Suramar storyline to awaken the Arcandor with about 4 hours of work (I didn’t track the time, and I was doing the Balance of Power questline at the same time), whereas that was about 4-6 weeks of time-gated progression before.
Shadowlands isn’t quite requiring the main to be time-gated, specifically, but locked the Renown progression to a weekly unlock so that if someone started NOW on it, they could complete the Covenant storyline within a week or two, as opposed to everyone who has been playing since Shadowlands launch.