I feel like this is a legitimate invitation to recommend where people should start watching Doctor Who.
And the answer is “Wherever you damn well please.” I’m sick of seeing people being shamed for skipping Nine or starting with Eleven. It’s a show about time travel, it isn’t exactly linear. And if your argument is that each Doctor informs the next one-well, yes, that’s true, but by the same logic, newbie Whovians should start with “An Unearthly Child” and the First Doctor.
A “true fan” will watch the Ninth Doctor’s run eventually, because they’ll search out more Doctor Who voraciously. They might even sample the Classic Doctors and fall hopelessly in love with them as well (as I did). Heck, they could have started with the Classic Who run.
You can start wherever and with whichever Doctor you like. For as long as you love the show, I’ll count you as a fellow fan.
As long as you don’t pretend that what came before doesn’t exist.