AFAICT the 5e SRD is basically worthless. It's not even good enough to build basic core characters.
Maybe check the popularity of the 5e Unearthed Arcana rules previews? They'd be roughly equivalent to the stuff at archive.wizards.com in terms of comparing 3.5e with 5e -- both would be a small fraction of the player base, but roughly the same sort of people so perhaps roughly the same fraction.