…complaining about how he makes them doubt and question all the gifts/blessings given to them by their god.
I fail to see how this is a problem.
That’s what Lucifer does—he drives personal growth by making you question everything. It’s your choice whether you use that doubt as hindrance or inspiration. So what if he brings up those uncomfortable questions regarding your loyalty or devotion to your god? He does it to his own devotees, too. And more often than not, those questions either lead to a renewed, more stable faith or one more suitable to your beliefs. Although he may not agree with the actions or mindset of your god, that doesn’t mean the doubts he plants are there to sever that connection—whether you want to be a devotee of that god is your choice and yours alone, which is ultimately the point he’s usually trying to get across in these situations. Unfortunately, a lot of times it seems that many are unable to see it as an independent choice, whether due to how they were brought up or taught to believe, or because of the concepts of sin and salvation that bind through guilt.
In short, healthy doses of skepticism, doubt, and uncertainty aren’t bad things—stop seeing them as personal attacks against yourself and your faith and use them instead to your advantage.