@nikitabier has made a counter point which I’ve come to appreciate which is that adding friction in onboarding is not always a bad thing. 

If it helps meaningfully with retention and engagement, it’s often worth doing. 

For us, requiring pfp only causes a 0.1% dropoff but makes real profiles look more legit and spammer easy to identify

This is as good as a rule at this point.
- an onboarding process that demands more attention has an inverse relationship with conversion rate and a direct relationship with retention and engagement. You have to find a sweet spot and prioritize what is important for you. 
But those extra onboarding steps need to be relevant for later engagement.

In contrast for example, an onboarding friction that does not lead to engagement: KYC stuff.
On some platforms it is an unavoidable step. I think KYC stuff still creates some imaginary barrier against leaving but when you do it you're not engaging with the core purpose of the platform. The forced actions do not initiate an engagement behavior.

In this case pfp is crucial to the entire experience on this site. A blank or randomly generated photo is the social media equivalent of boarded up windows. The act of uploading a photo, tho forced, is engagement with the core function of this site. It initiates a pattern of behavior of engagement.