Joshua Welsch’s review published on Letterboxd :
Rating doesn't really portray how much I like it. First Reformed demonstrates the similarity between religious fervor and political extremism, all while re-using the plot-and-character template of Taxi Driver. Its okay if Paul Schrader can only really make one good film over and over, because the template is still haunting and resonant as it first was. For those that don't buy the ending, again, this is nothing new. The bizarre editing choice (quick cut to black while cutting the accompanying music) draws what is visually portrayed into question.
So many elements of the film were amazing (Hawke's acting and monologues, the flat, depressing camera-work) its a pity that other elements (the obviously green-screened "mystery tour" scene, and the occasionally heavy-handed presentation) were not done as well.