The role of hormones (especially insulin) in regulating fat storage and whether stored fat is available to the body as energy is better understood now, and much has been documented about how high insulin combined with low calories over time results in a lowering of the metabolic rate (resulting in stalling weight loss and then weight gain) rather than sustainable weight loss.
Also "it's nice to believe you don't have to suffer to reach your goals" is a silly and moralistic thing to say. But it typifies the american "scientific understanding" of weight loss. Fat is immoral, suffering is virtue, therefore in order to lose your immoral fat you must suffer.
Just look at all the massive success of those in the IF and keto community in living joyful lives, not deprived, losing fat etc. etc. And then look at all the people for whom calorie counting has completely failed. The information is out there (shruggie)