Obama himself claimed - several times - that his DACA executive order was Unconstitutional. He's just virtue signalling to his Leftist base. 

Trump is simply undoing this Unconstitutional order and putting the issue in the hands of Congress - where it should be. Though I doubt Democrats will work with Republicans to solve this issue.  There are probably lots of Repubs who would be willing to work with them to legalize the Dreamers. But Pelosi and Schumer would rather keep this as a campaign issue. They have no interest in solving this problem. 

If you think Congress should act and they don't, your beef is with Congress, not Trump.