CIPF does not insure your securities... only really against fraud or the minor amounts in transition during a firm's insolvency (e.g., they held cash or were making a transfer to another account for you when they because insolvent.. or had shady accounting practices and "lost" your securities or you were a victim of embezzlement / fraud)
The core securities being held in your account, in your name, are fine... it is only the cash money at the "fringes" or outright scams / fraud that are insured by CIPF.
So, yeah, I might be hesitant with holding more than $1 million in a small, new, secondary brokerage, but not with one with a large established customer base and policies.
Maybe I am naive.