Can all decision problems reduce to undecidable?
a machine that for any input will never accept, but always loop forever


isn't a decision problem, and so it doesn't make sense to say it's undecidable.

However, given an undecidable problem $A$, there are always "more undecidable" problems $B$, i.e. those which would be undecidable even given an oracle for $A$. For example, the halting problem for Turing machines extended with an oracle for $A$.