The new version of the loop block is only able to work on an array from the result of a previous block. This works for most situations, except when polling. In the legacy version you were able to define the whole loop in JS instead of selecting an array:
Since you have to select a data source on the new Loop which contains values you wish to iterate over it's impossible to re-create the loop block above using the old loop with the new version. being able to select 'infinite' for the data source and define a condition to break the loop or re-adding the 'mode' selection for GUI/Code would both solve this, but as it is I'm unable to remove the legacy component