The Remain alliance of three parties may have limited impact. Sir John Curtice estimates that it could affect the outcome in six seats. Of course, that could be significant in a tight contest.
There is some anecdotal evidence that voters do not like their choice being restricted so that, for example, they can no longer vote Green. It has also been pointed out that the election is about more than Brexit.
Good analysis here, pointing out that Labour is key to the Remain Alliance achieving its goal: Conservative seats under threat