The main scenario is unlocks so much in this game, the decision makes sense.
I found the pre-50 story worse anyway because it had much more filler so that you could level mostly through the MS quests.

If those players don't like quest gating, this game isn't for them anyway because it's a clear design choice.

I think it's great that they're making post 50 content part of the vanilla leveling experience.
They can make the 50 quests give decent xp to compensate and tie into leveling. There might be ways to ease the transiton, not sure what they have in mind.