Samsung did the best job of anyone trying to differentiate their phones, and as such was the only profitable Android manufacturer for several years. But even they are losing market share rapidly to the likes of Xiaomi and Huawei and their profits have fallen off a cliff in the past couple years.
I think they're making great profits even if they pretend not to. Their prices are only slightly lower than Apple's very premium pricing and all they do is integrate components from other manufacturers (OS from Google, RAM from memory vendors, CPU from Qualcomm etc.). They are very similar to PC motherboard makers like ASUS and charging $200 to $700 per phone gives them plenty of profit.
It's just like the PC market where the multitude of motherboard makers have a small profit margin, whereas the few component makers for CPU, chipset, RAM, hard disks etc. make decent or fat profits.