Task dependencies! One can't even plan a wedding without this!
Dear Planner Team,
I work for a very large company that is in the process of rolling out Trello because Planner lacks this ONE feature.
We get it.
Microsoft needs to be careful not to cannibalize it's Project business.
That said, there are plenty of other vital features in Project that will sustain that product.
Have you never heard of the Innovator's Dilemma?
Allowing the low end of the market to be stolen out from beneath you is a very un-Christensen thing to do.